Tennessee Naturalist Program
Birds of TennesseeFeathered Fauna
Enhanced Study Guide
12/2014
Tennessee Naturalist Programwww.tnnaturalist.org
Inspiring the desire to learn and share Tennessee’s nature
These study guides are designed to reflect and reinforce the Tennessee Naturalist Program’s course curriculum outline, developed and approved by the TNP Board of Directors, for use by TNP instructors to plan and organize classroom discussion and fieldwork components and by students as a meaningful resource to review and enhance class instrucLon.
This guide was compiled specifically for the Tennessee Naturalist Program and reviewed by experts in these disciplines. It contains copyrighted work from other authors, illustrators, and publishers, used here by permission.
No part of this document may be reproduced or shared without consent of the Tennessee Naturalist Program and appropriate copyright holders.
2
Birds of TennesseeFeathered Fauna
Objec5ves Become familiar with strategies and techniques for field idenLficaLon of Tennessee bird species by sight and sound. Explore various aspects of bird behavior, habitats, adaptaLons, and conservaLon concerns.
TimeMinimum 4 hours – 2 in class, 2 in field
Suggested Materials ( * recommended but not required, ** TNP flash drive)• Peterson Field Guide to Birds of Eastern and Central North America, Sixth EdiLon, Roger
Tory Peterson *• Birds of Tennessee Enhanced Study Guide, TNP **• Field Checklist of Tennessee Birds (free TWRA card) • Binoculars
Expected OutcomesStudents will gain a basic understanding of 1. bird anatomy and adaptaLons 2. bird species that are year-‐round, summer, or winter residents and migrants in Tennessee3. categorical differences among bird groups: swimming, wading, game, prey, non-‐passerine,
passerine4. habitats, ecological niches5. bird funcLons and behavior – maLng, territory, nesLng, migraLon pa_erns and flyways, flocking, feeding6. physical idenLficaLon characterisLcs – size, silhoue_e, field marks, color pa_erns, flight
pa_erns 7. auditory idenLficaLon characterisLcs – songs and call notes 8. threats to birds and conservaLon concerns 9. CiLzen Science-‐type bird projects 10. binoculars and spoeng scopes
3
Birds Curriculum Outline
I. What Is a Bird A. EvoluLonary history and classificaLon B. Anatomy 1. physical properLes a. endothermic vertebrates b. wings c. feathers d. skeleton, beak, feet e. eggs f. syrinx g. addiLonal a_ributes
II. Bird Behavior A. Range 1. residents vs. transients B. MigraLon 1. Lming, mechanisms, moLvaLon 2. Tennessee flyways C. CommunicaLon 1. non-‐vocal sounds 2. calls: contact, alarm 3. songs: mate a_racLon, territory D. MaLng and nesLng 1. breeding 2. nest types and locaLon preferences 3. development and care of young E. MolLng and feather care F. Feeding
III. Bird Habitat A. Field, forest, and edge B. Water C. Ecological niches and funcLons 1. insect control 2. plant pollinaLon and seed distribuLon 3. predators and prey 4. bioindicator
4
IV. Bird IdenLficaLon A. General physical appearance 1. size, shape, silhoue_e 2. tonal pa_ern and color B. Behavior C. Habitat D. Field marks E. Songs
V. Birds of Tennessee A. Orders of birds B. Non-‐naLve species C. Rare species
VI. Threats to NaLve Birds A. Development and landscape alteraLon B. Forest fragmentaLon C. Non-‐naLve invasive plant species D. PolluLon and li_er E. Predators, parasites, and compeLLon F. Disease G. Manmade structures H. Disturbance
VII. Birding AcLviLes A. Bird counts and banding B. Bird watching 1. binoculars and scopes C. Backyard habitats
VIII. Resources A. PublicaLons B. OrganizaLons C. Internet
VIX. Review QuesLons
5
I. What Is a Bird
Evolu5onary History and Classifica5on
Birds are descended from repLles as evidenced from the anatomical features they share and mostly likely evolved from dinosaurs. Following the mass exLncLon that eliminated dinosaurs (65 Ma), precursor species to the modern bird mulLplied. By five million years ago, most current bird genera had emerged. During their evoluLon, birds had to develop two key elements -‐-‐ feathers and endothermy (internal body heat). Feathers are their airfoil for flight, and endothermy supports high energy processes necessary for the rapid muscular acLon of flapping. Classified within the animal kingdom (Kingdom Animalia) and joining other vertebrate species such as mammals, repLles, amphibians, and fishes in the Phylum Cordata, birds are grouped in the Class Aves. Several characterisLcs are considered in determining their relaLonships:
• form or appearance (plumage color, body shape, anatomical structures)• behavior (vocalizaLons, display, nest structure, breeding)• biochemical (molecular proteins, enzymes, mitochondrial DNA, nuclear DNA)
ClassificaLons in the American Ornithologists’ Union Checklist of North American Birds build upon a species definiLon of “interbreeding natural populaLons that are reproducLvely isolated from other such groups.” This definiLon has persisted despite problems posed by differing species that do interbreed successfully and widely spaced species lacking any definite proof of breeding incompaLbility. This checklist is conLnually revised to reflect the dynamic nature of bird study and DNA development.
Bird Anatomy: Unique Physical Structures
As endothermic vertebrates, birds have a backbone and generate their own body heat, traits they share with mammals. Many birds’ metabolic rates are similar to mammals, but passerines (perching songbirds) may have rates 30 to 70 percent higher. Body temperatures are typically around 104 degrees. Chemically, this high metabolism and internal heat allows faster processing of informaLon through nerves and muscles speeding reacLon Lmes, an important survival adaptaLon. Birds employ various strategies to conserve or release excess heat as needed. In cold weather, they fluff feathers to increase insulaLng properLes. Exposed legs and feet serve as heat exchangers in warm weather and are nestled into the birds’ breasts when cold. Sunning with spread wings reduces energy spent on internal heat, though this behavior is also
6
associated with other needs. ResLng in the shade during hot aoernoons and respiratory panLng keeps passerines cooler. Birds that soar use rising air thermals to reach cooler alLtudes. Unique physical structures define birds as an organismal group. No other animals have feathers. Their ability to fly, a trait shared with some invertebrate groups and bats (mammal), is due to wings, feathers, lightweight skeletons, and other internal physiological traits. Birds are the only endothermic species to lay eggs. Their feet are adapted to several special purposes. Different beak designs help them exploit a wide variety of food and habitat types, reducing species compeLLon. A special vocal apparatus allows songbirds (oscines) to produce remarkably varied and complex vocalizaLons.
Acadian Flycatcher, held in the “bander’s grip” during bird banding (Margie Hunter)
7
Wings The mechanism allowing bird flight is a complex combinaLon of wing shape, bone structure, and a series of feather adaptaLons and adjustments providing the thrust and lio necessary to become and remain airborne. A wing’s shape -‐-‐ thicker on the leading edge and narrowing with a slight downward curve -‐-‐ creates an ideal airfoil, and a tapering Lp reduces air turbulence. Flapping, akin to a plane’s propellers or jet engine, provides thrust to generate forward movement. Forward moLon produces the airflow over and under the wings necessary to iniLate lio. The orientaLon of primary flight feathers adjusts during wing strokes to maximize thrust and reduce drag. Birds manipulate their wings’ angle to fly at slower speeds and to induce ‘stall’ upon landing. For different species, variaLons in wing-‐loading (the bird’s body weight per unit of wing area) and aspect raLo (the wing’s length relaLve to width) affect flight behaviors such as flapping, speed, gliding, and how long the bird can stay aloo.
Feathers Birds are the only organisms with feathers, which are instrumental in flying, temperature regulaLon, maLng displays, and camouflage. Complex feather anatomy produces a strong yet very lightweight structure. A feather usually consists of a central shao with vanes to either side. The shao’s end near the bird’s body, called the calamus or quill, contains no vanes and is hollow. The shao secLon supporLng the vanes, called the rachis, is solid. Vanes are composed of parallel branches called barbs. Each barb is lined with short branchlets called barbules. Barbicels (Lny hooks) at the ends of barbules lock the barbules and barbs together for strength. On flight feathers, a narrow outer vane is the leading edge in flight, and the inner vane is wider such that each feather creates its own ideal airfoil curve. Birds possess three main types of feathers: flight, contour, and down. Flight feathers on the wings, called remiges, help the bird become and remain airborne. Outer remiges are “primaries,” the largest and strongest feathers a_ached to the wing’s end which provide thrust on the downstroke. These feathers separate and rotate slightly on the upstroke, allowing another measure of forward thrust. The number of primaries varies by species from three or four to sixteen. Inner remiges are “secondaries,” located between the primaries and the body, and can be as few as six or seven or as many as 40 relaLve to body size. Secondaries remain solidly locked together to provide lio when flapping or soaring. Retrices are tail feathers a_ached to the fused tail bone. They provide flight stability and control. Contour feathers follow the bird’s overall shape to cover the body and impart color. Overlapping like shingles, contour feathers keep the bird dry and are controlled by special muscles that adjust their posiLon (such as when fluffing) and maintain a smooth surface. Layers of contour feathers called coverts overlap the edges of remiges and retrices above and below the wings and tail to streamline their shape and add insulaLon. Down feathers lie underneath the contour feathers to keep birds warm. Their soo fluff results from a reduced or missing rachis and no barbules or hooks. This fluff creates air pockets
8
forming an insulaLng layer next to the skin. Similar to down, semiplumes are another type of insulaLng feather. There are other specialized feather types including bristles. Some insect-‐eaLng birds, such as flycatchers, Whip-‐poor-‐will, and American Robin, have rictal bristles projecLng around their beaks, usually at the base. Small feathers with a sLff rachis and few barbs, their purpose may be to protect birds’ eyes from wriggling insects and could provide tacLle informaLon much like whiskers. Pigments in feathers account for most of the colors. Melanins produce black, grays, and tans. Carotenoids make reds, oranges, and yellows. Porphyrins are mostly brown but can also be red or green. Blues and iridescence, however, are structural colors produced as light bounces off the feather’s shape and composiLon. Some greens may be structural in nature too. Images of feather anatomy may be found at the Cornell Lab of Ornithology Web site: h_p://www.birds.cornell.edu/AllAboutBirds/studying/feathers/feathers/document_view
Examining the flight feathers of a Black-‐throated Green Warbler during banding (Margie Hunter)
9
Skeleton To lighten weight, the bones of most birds species are hollow. To withstand the stress of flight, hollow bones contain a system of internal braces for structural strength, and smaller bones in the wing, pelvis, and leg are fused. All birds posses a furcula, two collarbones that are fused into what is commonly called the wishbone. PosiLoned within the thorax or chest cavity, it flexes during flight which may serve as an aid to respiraLon and wing strokes. A bird’s neck contains two to three Lmes the vertebrae of mammals to allow needed flexibility for preening or observaLon of surroundings. In contrast to these lightweight bones, muscles used in flight may account for 20 to 25 percent of a bird’s total body mass.
Beak Bony jaws coated with keraLn form the bird’s beak (or bill). As it wears, the keraLn coaLng is replaced to keep beaks in top working order. Many modificaLons of beak shape and size allow species to be_er exploit an environment or food source. Different beak types are suited to glean insects from foliage, probe wood or mud, pry tree bark, crack tough seed coats, tear flesh, or filter food from water. Beaks best suited to one type of food ooen prove less adept at others. They appear rigid, but many beaks have some degree of flexibility to improve dexterity. Tongues are ooen highly modified too, and birds’ digesLve systems must compensate for their lack of teeth. Winged forelimbs require beaks to serve as more than a mouth. They are mulL-‐tools used for a variety of tasks beyond feeding. These other uses are just as important -‐-‐ building or excavaLng nests, turning eggs, preening feathers, climbing, defending against or a_acking enemies, and maLng displays. In modern applicaLon, the terms beak and bill are used interchangeably with most birds, though beak is parLcularly used regarding birds of prey and bill most frequently with hummingbirds, pigeons, wading and swimming birds. Such disLncLons, however, are unofficial.
Feet and Legs Birds are bipedal, and the leg length and girth and the feet of different species reflect their life histories. Long, thin legs and parLally webbed feet on wading birds help them negoLate shallow water and mud. Thick, powerful legs and sharp taloned feet of raptors enable them to clasp, kill, and carry their prey. Water birds use their webbed feet as swimming paddles. Like their beaks, bird’s feet have mulLple uses -‐-‐ stand, walk, run, hop, clasp, climb, carry, catch, preen, scratch, wade, or swim. The skin of their feet is heavily scaled for protecLon. Composed mostly of tendons and bones, bird feet have few nerves, muscles, or blood vessels and can withstand exposure with li_le discomfort. What appears to be a bird’s foot is really its toes. Birds stand on their toes. With many birds, parLcularly the passerines or perching birds, each foot has three toes poinLng forward and one toe (the equivalent of a human’s big toe) poinLng to the rear. This arrangement, called anisodactyl, allows them to securely clutch a branch. With some bird groups, the back toe is greatly reduced.
10
A few bird groups have their toes in a zygodactyl arrangement -‐-‐ two toes forward, two toes back. This orientaLon helps woodpeckers and cuckoos cling verLcally to tree trunks. Owls are zygodactyl, but their third toe can rotate to the front or rear as needed.
Eggs Other vertebrate groups -‐-‐ repLles, fishes, mammals -‐-‐ have at least a few species that give birth to live young. All birds lay external, amnioLc eggs in reproducLon, which minimizes the weight toll on breeding females’ flight. Given necessary warmth, young develop inside hard-‐shelled eggs. Egg shape, size, and markings, clutch size, and incubaLon Lme vary by species. Some young are precocial -‐-‐ grouse, quail, water and shore birds, developing fully inside the egg to hatch with down feathers and the ability to run and feed themselves. Young of songbirds, hawks, herons, and other groups hatch when they are sLll helpless -‐-‐ naked, blind, weak. These altricial nestlings require intensive parental care.
Syrinx Birds vocalize through the syrinx, a structure comparable to the human larynx, by forcing air through the trachea which vibrates thin membranes. Far more efficient and elaborate, however, the syrinx uLlizes the vast majority of the air, moving it through two separate tracheal tubes, each of which can create an individual sound simultaneously, termed “dueLng.” A complex system of muscles, parLcularly in the passerines, creates the diversity of sounds they produce in songs and calls.
Addi5onal AMributes and Characteris5cs Birds have very acute vision (two to three Lmes sharper than humans), excepLonal hearing (parLcularly nocturnal species such as owls), and a reasonable sense of smell (Turkey Vultures locate fresh carrion by smell), but few taste buds. Their digesLve systems are highly efficient. Like repLles, they excrete nitrogen as ureic acid rather than the more toxic urea of mammals. White ureic acid and darker undigested waste form semi-‐solid droppings.
11
II. Bird Behavior
Various bird behaviors may be seasonal in nature -‐-‐ breeding, migraLng, molLng. Others, such as feeding, preening, and bathing are daily or regular maintenance acLviLes. Some of these behaviors are or can be social in nature involving communicaLon and contact with other individuals, such as flock feeding.
Range The range of a species reflects the geographic area or region within which it is found and can be described using poliLcal boundaries or geographic features. Ranges may change over Lme, dependent on the introducLon of other species or the increase or decrease of suitable habitat. MigraLon pa_erns are factored into birds’ ranges which may show the wintering area widely separated from summer breeding grounds. Non-‐migraLng birds overwinter and breed in the same geographical area and are considered year-‐round residents. Migratory birds may be summer residents only breeding in the area, winter residents only resLng in the area between breeding seasons, or transients traveling through the area in route to their breeding sites (spring migraLon) or wintering grounds (fall migraLon).
Migra5on Timing, Mechanisms, Mo5va5ons MigraLon is an annual, seasonal event that follows predictable pa_erns among bird species. Seventy-‐five percent of North American nesLng bird species exhibit some degree of migratory behavior: long-‐distance (between conLnents), short-‐distance (within the conLnent), or elevaLonal (lowlands to mountains). Different breeding and wintering locaLons, maLng and nesLng habits, and migratory flight courses produce a wide variety of migraLon calendars among species. Day length is considered a prime trigger for migraLon, iniLaLng a series of hormonal responses in spring to prepare for the journey and breeding. In late summer, decreasing daylight shuts down the hormones to end breeding and spur preparaLon for fall migraLon. While most species’ migraLon pa_erns and Lming are fairly precise, there can be some variability. Weather, winds, and food supplies may delay or prompt early departure by a few days. Species may disperse over a broader area when traveling, and a few display differences based on age and sex (differenLal migraLon) -‐-‐ young males may remain closer to the breeding grounds to be the first back in spring and older females fly further south to more reliable wintering grounds. When all individuals of a species migrate from breeding areas to geographically separate wintering areas, it is called complete migraLon. In some species, individuals may elect to stay in the breeding habitat and not migrate with others to different wintering grounds, a pa_ern that is ooen the result of overlapping winter/breeding ranges where the species are found year-‐round. This is termed parLal migraLon. Irregular movement pa_erns that are not seasonal and
12
annual, called irrupLons, are typically triggered by some pressure associated with habitat, such as extreme weather, scarce resources, or overpopulaLon. PreparaLons for migraLon include a fat-‐rich diet. Fat is the best fuel, releasing twice the energy of carbohydrates or protein, and its metabolism yields water to combat dehydraLon. Long-‐distance migrants add as much as 50 percent of their body weight in fat, which fuels three to four days of flying, a distance of 1,800 to 2,500 miles. Before migraLon, some birds experience a complete molt to acquire fresh, aerodynamic feathers with less drag. The primary feathers of migrants are longer and more pointed to reduce air resistance. Birds tend to Lme the start of their journey when wind direcLon and speeds have become favorable, avoiding head-‐ and crosswinds in preference to tailwinds, and changing alLtudes to take advantage of favorable winds if warranted. Species that fly in formaLons assist each other, receiving boosts from the rising air currents generated by neighbors’ wings. Diurnal migrants, such as hawks, migrate during the day. Soaring species depend on thermals, rising pockets of warm air generated by the sun, to lio them into the air where they can glide to the next thermal with minimal wingbeats. Some non-‐soaring birds, like swallows and blackbirds, Lme their flights from predawn through the morning hours and perhaps again in late aoernoon. Night migraLon (nocturnal migrants) favored by songbirds offers many advantages -‐-‐ less predaLon threat, cooler temperatures, less atmospheric turbulence -‐-‐ for steadier, less taxing flights. MigraLng birds travel hundreds to thousands of miles each year to arrive at very specific locaLons. They must orient themselves in the right direcLon and navigate a course, employing several strategies in the process: sun polarizaLon, star posiLons, and the earth’s magneLc field. Sunlight is mostly sca_ered but polarizes in an arc 90 degrees from the sun’s locaLon. Birds use this polarized arc of light to fix the sun’s posiLon and their direcLon. The fixed posiLon of stars and their rotaLon around the North Star, provide a stable point of reference at night. Birds’ ability to sense the Earth’s magneLc field is of parLcular value to long distance migrants. Most birds posses an innate knowledge of their migraLon route. A few species, such as Sandhill Cranes, must be taught the route from parents and other adults in the flock. Once headed in the proper direcLon, it is believed birds navigate their course using geographical features -‐-‐ coastlines, mountains, rivers -‐-‐ as primary guides through most of the flight. Near their desLnaLon, they may rely more on local landmarks and even smell to locate specific sites. Given the energy needed and associated risks, these long journeys must convey real benefits to migraLng birds. Spring migraLon northward presents several advantages.
• Seasonally abundant food supplies• Reduced compeLLon• Longer days to forage• Avoidance of frequent nest predators and parasites common in the tropics• Larger and more frequent clutches
Fall migraLon south avoids the harsh weather and limited food supplies in northern areas during winter. Species that do not migrate possess the ability to exploit varying food sources through the seasons.
13
The dangers of migraLon are significant. Inadequate food, starvaLon, stopover habitat loss, predators, storms, hunLng, electric light disorientaLon (disrupLng star navigaLon), and collisions (buildings, wind turbines, etc.) take a high toll. Species could suffer yearly mortality esLmates as high as 60 percent.
Migratory Flyways in Tennessee The Mississippi Flyway covers the majority of Tennessee up to the Blue Ridge Province. Nearly half of the bird species in North America and 40 percent of the conLnent’s water birds spend some Lme in the Mississippi flyway extending from the boreal tundra of Canada to the southern Lp of South America. Changes in the last century to the Mississippi River drainage have negaLvely affected this flyway. Confined to less than ten percent of its original floodplain, wetlands associated with the river conLnue to disappear each year. The delta system, a criLcal stopover for migraLng birds, is imperiled. In Tennessee, NaLonal Wildlife Refuges and state-‐owned Wildlife Management Areas provide important pockets of protected habitat for migratory birds. Reelfoot Lake in Obion County, a NaLonal Wildlife Refuge, serves as a major stopover and wintering area for migrants within its bo_omland forests and open water. Other NaLonal Wildlife Refuges are centered in the state’s western third (Chickasaw, Hatchie, Lower Hatchie, and Lake Isom) and around Land Between the Lakes (Cross Creeks and Tennessee) featuring mature forests, intact riparian corridors, and open water. Even areas as small as Radnor Lake State Park and Natural Area in Nashville offer welcome opportuniLes. Numerous Wildlife Management Areas are spread throughout the state. NaLonal Audubon Society’s conservaLon priority list for the Mississippi Flyway targets 3.5 million acres of habitat and 17 species including these Tennessee birds: Li_le Blue Heron, Piping Plover, Short-‐billed Dowitcher, Sanderling, Ruddy Turnstone, Least Tern, and Western Sandpiper. The AtlanLc Flyway follows the eastern coastline from the North AtlanLc through the Caribbean to South America. It extends far enough west to encompass upper East Tennessee and the Blue Ridge Province along the North Carolina border. This narrow flyway is just one-‐tenth of the country’s land mass, yet it contains one-‐third of the U.S. populaLon and accommodates over 500 bird species. ConLnued development, agriculture, overfishing, and climate change pose threats in this corridor. Audubon’s AtlanLc Flyway conservaLon priority species list includes: Wood Thrush, Wood Stork, Semipalmated Sandpiper, Prothonotary Warbler, Grasshopper Sparrow, Golden-‐winged Warbler, Common Tern, Cerulean Warbler, Canada Warbler, Black-‐throated Blue Warbler, Bald Eagle, and American Woodcock.
h_p://conservaLon.audubon.org/mississippi-‐flyway h_p://conservaLon.audubon.org/atlanLc-‐flyway
14
Communica5on Birds communicate through several different of means -‐-‐ plumage, behavior, vocal sounds, and non-‐vocal sounds -‐-‐ for a variety of purposes.
Non-‐vocal sounds Noises from beaks or wings can send signals to potenLal mates or rivals. Some bird species may clack their beaks, and woodpeckers drum hollow logs or other resounding structures. Ruffed Grouse cup and flap their wings, creaLng a low frequency “thump” as the air compresses. Other species, like Wilson’s Snipe and some hummingbirds, adjust wing or tail feathers to produce whistling, ra_ling, or buzzing sounds when they fly. Calls Calls tend to be short, simple notes that serve a specific funcLon. Unlike songs which are mostly learned, birds have an innate understanding and command of calls. There may be as many as a dozen different calls tailored to specific communicaLon needs. Breeding pairs stay in touch with contact calls throughout the day to pinpoint their locaLons. Each can idenLfy the voice of its mate. MigraLng birds, those that fly in formaLons and at night, u_er flight calls to keep the flock together. Baby birds use a begging call to ask for food. Full-‐grown fledglings out of the nest can solicit parental responses with that call. Swallows issue a call when they find insect swarms to help each other locate food sources. The presence of a predator or other sudden disturbance will elicit alarm calls. These calls signal mates and young as well as other birds and taxonomic groups prompLng them to take cover or assemble to mob the intruder. Alarm calls not only warn of danger but also signal the predator that it has been spo_ed and its likelihood of success is now diminished. It is ooen difficult to pinpoint the bird giving an alarm call, a property that masks the bird’s locaLon from the predator. Songs Bird songs can be remarkably complex and beauLful and reach their pinnacle in the passerines or perching birds, Order Passeriformes. There are two suborders of passerines, Passeri or oscines, the songbirds, and Tyranni or suboscines, primarily the flycatcher family. Oscines use their elaborate syrinx to crao one or more phrases of musical notes, warbles, trills, buzzes, and other sounds into a signature song (or songs) for each species. The songs of oscines must be learned. Suboscine species have less complexity in their songs, which are innate. Environments have influenced the evoluLon of birds’ songs. Loud, low frequencies work best in dense thickets; loud, ringing songs are needed to overcome the noise of a swio stream or waterfall; buzzy, complex vocals distort less than sustained sounds in open grasslands. A species’ song may vary regionally, creaLng dialects. These dialectal variaLons can even be found on more local scales.
15
Birds spend a large part of their Lme singing during breeding season, repeaLng the songs perhaps thousands of Lmes in a single day. These unique songs, sung by males, have a dual purpose: to a_ract a mate and establish breeding territory. Mate A_racLon: Male songbirds seek to impress females, ooen through colorful plumage and/or their vocal skills. Both are designed to communicate their status and superior fitness as a prospecLve mate. Many birds have more than one song and conLnue to add to their song repertoire throughout their lives. Older males with mulLple songs adverLse their survivorship, experience, and health. Tennessee’s state bird, Northern Mockingbird, is a mimic that learns the songs of other bird species and throughout its life develops a stock repertoire of up to 300 different phrases including the sounds of other animals and inanimate objects like squeaky hinges. The related Brown Thrasher improvises variaLons of phrases numbering into the thousands. These large repertoires signal quality to females and help deter rivals at the same Lme. Territory: The song may sound the same to the indiscriminate ear, but the message received by other males is decidedly different from females. Birds stake and staunchly defend their breeding territories, patrolling the boundaries and using their songs to delineate their turf. This acLon is primarily directed against other individuals of their species, though some will also defend against closely related species, parLcularly if they need similar food resources or might interbreed. Males quickly learn the songs of their neighbors and react strongly to the presence of a ‘stranger.’ Nonbreeding territories may be established to protect food resources. “Full funcLon” sites serve both nesLng and food needs. Some birds sing with greater persistence if their territories are well stocked with food. Establishing these territories may confer another advantage by spreading birds out, thus making it harder for predators to fix their image and locaLons. Early morning Lming of the ‘dawn chorus’ may result from several moLvaLons. Light levels before sunrise are too low for effecLve foraging, but important social interacLons can take place. Early, vigorous singing signals health and vitality to mates and rivals. Songs at this Lme are clearer and more consistent, allowing neighboring birds to be_er fix their territories and learn each other. There is also less distracLon from other typical dayLme noises. It also doesn’t hurt that atmospheric condiLons are usually cooler and calmer. Different species begin singing at different Lmes; thrushes are among the earliest. [h_p://www.wired.com/2014/03/birds-‐sing-‐morning/]
16
Ma5ng and Nes5ng
Breeding The breeding plumage, or alternate plumage, of many species’ males differs from their basic plumage and requires a parLal molt to grow these feathers. Plumage signals work best when they are most conspicuous -‐-‐ bright colors, isolated color patches, head stripes, or tail markings. Color patches may serve another purpose as well, situated where they can be suddenly revealed for a startle effect or to direcLon a predator’s a_enLon away from the bird’s body. The bright colors and pa_erns of alternate plumage are designed to a_ract mates. As with brilliant singing, plumage color is ooen a sign of health and the ability to forage effecLvely for food or establish good territories. Some females, however, look past the vocal and visual bravado to judge a prospecLve mate directly on the quality of his nesLng territory. Various movements and postures are employed by most bird species in courtship behavior. These behaviors involve such acLons as head-‐bobbing, bowing, sky poinLng, wing displays, or breathtaking aerial displays, ooen in highly ritualized combinaLons. Displays may also be used in aggressive confrontaLons with rivals, though ooen these acLons are more bluff than any real threat of physical conflict. Males engage in courtship feeding, bringing food to the female, as the pairs are becoming established, and this behavior may conLnue into egg incubaLon, providing needed nutriLon for successful breeding. Males’ singing is thought to sLmulate females’ ovaries, egg laying, and nesLng building acLviLes. The majority of all bird species, 90 percent, are socially monogamous, (co-‐operate in raising young), but they may not be geneLcally monogamous. Each partner may mate with others, a behavior termed extra-‐pair copulaLons, to spread genes (males) or hedge bets with be_er males (females).
Nest types and loca5on Bird nests are designed to hold eggs and provide shelter, reflecLng habitat preferences and reproducLve needs of the species. Nest building is insLnctual, but skill in construcLng complex nests and choosing materials and appropriate sites must be honed. Some birds species use nest building skills to a_ract a mate. There are several different types of nests, and sizes range from a hummingbird’s 1.5-‐inch diameter cup nest to the massive plaxorm nest of a Bald Eagle, eight feet wide by 13 feet deep weighing a ton or more. Ground nests -‐-‐ Many non-‐passerines do not construct nests. Ground nesters with precocial young lay their eggs on the substrate or may make minor scrapes in the soil, someLmes with a thin layer of materials as padding. Ground scrapes are made by rotaLng the bird’s abdomen in the dirt. Many shorebirds use this nest type. Ground nesLng requires parents to spend more Lme on the nest to keep eggs warm.
17
Plaxorm nests -‐-‐ Plaxorm nests are usually loosely woven sLcks with a depression in the center, placed in tree branches or on other structures elevated off the ground. Ospreys, herons, eagles, and cormorants construct plaxorm nests. Cavity nests -‐-‐ ConstrucLng their nests inside a tree cavity or a man-‐made box, cavity nesters, such as Eastern Bluebird, Prothonotary Warbler, and woodpeckers, are concealed from predators and protected against inclement weather. The birds may even select sites with an opening oriented away from cold winds (or hot sun) and toward warm sun (or cool breezes), and shio the orientaLon between the first and second broods as seasonal weather condiLons change. Cupped nests -‐-‐ The standard image of a bird’s nest, cups are the most solid and complex type of nest construcLon, displaying tremendous variety in size and shape. Cups may be suspended from tree or shrub branches, a_ached to fixed structures such as a house porch or gu_er downspouts, or sited on the ground in a meadow or prairie. Other nest types – Kingfishers and Bank Swallows excavate underground burrows in verLcal banks. Cliff Swallows construct enclosed nests a_ached to a cliff face, bridge, or building eaves. More than two-‐thirds of passerines construct open nests (as opposed to caviLes or domed structures), perhaps to keep the nests small and less obvious. Use of materials that blend into the site or placement on thin outer branches, reduces the chance of predaLon.
Dark-‐eyed Junco with nesLng material, Great Smoky Mountains NaLonal Park (Margie Hunter)
A variety of nest materials help cushion, insulate, and safely cradle the eggs, including grasses, leaves, twigs, branches, snake skins, cow pies, animal hair or fur, shells, lichens, ribbons, and Lnfoil. Binders such as mud, spider or caterpillar silk, or leaf mold help hold the nest together, and many of these materials add a measure of waterproofing. The nest is ooen
18
lined with feathers from the female’s brood patch, the lower secLon of the belly. Removal of the feathers allows her body heat to more effecLvely incubate the eggs and warm the babies, and the feathers add an insulaLng layer to the nest. Other fine materials such as mosses, grasses, leaves, conifer needles, hair, and fur may be used. Certain bird species may add cedar bark or fresh leaves of plants known to repel insect parasites. SanitaLon is important and parent birds remove the fecal sacs of their young to keep the nest clean. A few bird species are known to pair with other organisms such as bees and wasps or ants for assistance with pests and predaLon. House Sparrows and kingbirds may nest next to raptors. The predatory birds do not hunt close to their own nests and benefit when the li_le birds warn of intruders.
Development and care of young Eggs are remarkable structures of protein and calcium carbonate designed to provide everything the developing bird embryo needs from ferLlizaLon unLl the chick hatches, essenLally a self-‐contained womb. Eggs must withstand the weight of the parent, prevent dehydraLon, allow permeaLon of oxygen, and protect the developing embryo from most harm. Bird eggs consist of the ovum and a series of layers of albumen inside an external shell with internal membranes. The ovum, commonly called the yolk, is a single-‐celled structure. The embryo forms from a ferLlized blastoderm (spot) on the ovum, and the remainder of the yolk provides the embryo with nutrients. An egg’s shell allows an even exchange of gases to support the growing chick as healthy oxygen replaces waste gases. Without this capability, chicks would suffocate. Baby birds require acLve parental care before hatching. Warmth is essenLal to normal development of the eggs, which require temperatures at or just below 100 degrees. Birds with webbed feet may use them to warm eggs, but most species sit on the eggs, enhancing the heat transfer through an exposed area of skin called the brood patch. The majority of these shed brood feathers automaLcally; ducks and geese pluck theirs. Birds with altricial young keep the brood patch for a Lme beyond hatching to warm the naked nestlings. If both parents brood, the male may develop a brood patch too. IncubaLng eggs is delicate business. Birds sense the eggs’ temperature and Lme the length of brooding relaLve to air temperature. Eggs must be turned periodically to warm evenly. Varying by species, turning may be done as ooen as every eight minutes up to once an hour. Eggs cannot be allowed to get too warm either, and shading from the sun is important in open nests. IncubaLon may last as long as two weeks or more depending on the species. Clutch size represents the number of eggs in a single nesLng. Passerines typically average two to five eggs per clutch. Waterbirds and gamebirds may triple those figures. Many species lay more than one clutch and can breed again if a clutch or brood is lost. Colors and pa_erns on bird eggs help conceal them from the view of predators or nest-‐parasite species like cowbirds. ProtecLon from predators may involve distracLon displays to draw a_enLon away from the nest or physical a_acks. SomeLmes, several birds gang up on a predator, a behavior called mobbing.
19
When fully developed, the young chick makes one of the most strenuous journeys of its life…hatching from the egg with the aid of two specialized structures. A sharp “egg tooth” develops on the Lp of the upper beak, and a substanLal enlargement of the muscle at the nape of the chick’s neck, someLmes called the “hatching muscle,” helps brace and cushion the chick’s neck. Hatching may take hours or days and is usually Lmed to coincide with morning, giving parents a chance to feed the babies before dark.
Dark-‐eyed Junco nest built into the side of a trail in the Smokies (Margie Hunter)
As menLoned earlier, there are two main categories of hatched young: precocial chicks and altricial chicks. Precocial chicks, such as Wood Ducks and Sandhill Cranes, have open eyes, a thick covering of down, and can feed themselves. They become strong enough to leave the nest within two days. Altricial chicks are blind, naked, weak, and unable to maintain body temperature. Their closed eyes, lack of down, and inability to move on their own make them totally dependent on their parents for survival. Songbirds, raptors, herons, hummingbirds, and many other groups have altricial young. Parents must brood the young to keep them warm, clean the nest of droppings, and typically share the duLes of feeding nestlings. There are degrees of precocial and altricial development between these two extremes based on which traits they do or do not posses at hatching. For example, some semi-‐precocial birds must be taught what to eat and how to get it. Female parents of precocial birds invest much more energy into their eggs for greater development pre-‐hatching. Young of these species are ooen raised by one parent. Parents of altricial young are socially monogamous as both are needed to help dependent nestlings
20
become self-‐sufficient fledglings, a fairly rapid process lasLng about two weeks for most songbirds. With most bird species, breeding is Lmed so young hatch and grow when insects are most abundant. Adults that normally feed on vegetable ma_er (fruit, seeds, etc.) eat insects for the high protein value during breeding and feed them to growing nestlings. Some species bring relaLvely intact insects back to the nest; others swallow the food and regurgitate it for the babies. Nestlings’ special begging call and their brightly colored, gaping mouths spur parents’ strong insLnct to feed their young. Upon fledging, males may take responsibility for some or all young, allowing the female to prepare for another clutch.
Feeding Searching for food is Lme consuming and energy taxing, which explains why birds go to such lengths to stake and defend good territories and return to them in subsequent years. They have already learned the best places to search and can forage more efficiently. Territory size may reflect the nutriLonal needs of the species and the abundance of food. Rich sites can support smaller, more numerous territories; poor sites require larger areas. Birds may change their diet at different Lmes of year, e.g., from insects to fruit, based on locaLon and availability. InsecLvores ooen briefly specialize in one or more insects during peak abundance then switch to others through the season as populaLon numbers of different prey wax and wane. Birds form “search images” to help them detect camouflaged insects. They can carry a quanLty of food in their crop, a muscular pouch in the esophagus, to digest at leisure, cache, or feed to young. Birds recall the locaLons of cached food based on landmarks. By dipping their beak in water and Lpping the head back to swallow, birds drink to replace moisture lost through respiraLon and defecaLon. Carbohydrates and fats (lipids) are the main sources of energy. Lipid-‐rich foods are essenLal to build fat stores for migraLon. Proteins build Lssues, essenLal for reproducLon, growth of young, and feather producLon. One of the main sources of protein is insects. Many birds that typically eat fruit, sip nectar, or crack seeds will switch to insects during breeding season for themselves and their young, whose diets are almost exclusively insects. The Lming of breeding season corresponds to theses sources of readily available protein. Calcium, important for breeding females’ egg producLon, is obtained just before laying by consuming certain insects including snails. Raptors and other predatory birds face the challenge of catching evasive animal prey. Talons and sharp or hooked beaks are used to spear or subdue and kill. Even insect-‐eaLng birds may have to wrestle with uncooperaLve food and manipulate it to remove wings or legs. Birds quickly learn which food sources are palatable which induce nausea, like the Monarch bu_erfly. They must disLnguish among various types of fruit, gauge ripeness, and judge nutriLonal value.
21
Outside breeding season, flocks of mixed bird species help each other by feeding more efficiently in these groups, parLcularly when food availability is low. Benefits include more eyes foraging, one species flushing prey for another (commensal feeding), reduced compeLLon given varying food preferences, an opportunity to learn new food sources, and the strength and safety inherent in numerous individuals funcLoning as a group. There are terms for animals with different food preferences. Birds typically fall into more than one of these categories.
• InsecLvore -‐-‐ insects• Frugivore -‐-‐ fruits • Granivore -‐-‐ seeds• Nectarivore -‐-‐ nectar (hummingbirds)• Carnivore -‐-‐ meat (raptors, owls)• Piscivore -‐-‐ fish-‐eaLng carnivore (herons, kingfishers, eagles)• Herbivore -‐-‐ plants (waterfowl)• Scavenger -‐-‐ carrion or refuse (vultures) • Omnivore -‐-‐ a variety of different food types (gulls)
Mol5ng and Feather Care Parasites, fungi, bacteria, and wear take a toll on feathers. Preening feathers maintains their appearance for plumage displays and insulaLng, waterproofing, and aerodynamic properLes.To preen, a bird fluffs its feathers and combs through them with its beak aligning and interlocking them. The bird exudes waxy oil from a gland near the base of its tail to spread through the feathers. This oil prevents the feathers from drying out and may deter parasites and pests. Places out of reach of the beak are scratched with the foot. Much Lme and energy is devoted to this regular task, and even more is required to prepare newly emerging feathers during molt. Worn feathers must be replaced, and birds will lose the old feathers and grow new ones, usually once a year, in a process called molt, or moult. There is no definiLve progression or Lming for this process. The molLng pa_ern -‐-‐ full or parLal, which parts of the bird, and Lme of year -‐-‐ varies among species. Species that live in dense thickets suffer more feather wear and molt twice a year. In late summer or early fall before migraLon, some birds experience a complete molt, replacing all their feathers. An energy intensive process that leaves the bird vulnerable, molLng occurs at a Lme when food is plenLful and other acLviLes are light. Breeding, or alternate, plumage is shed and all birds, male and female, grow their basic plumage. In spring, males with colorful breeding feathers undergo a parLal molt to grow their alternate plumage. Females retain their basic plumage year-‐round. This gender difference in the birds’ coloraLon is termed dimorphism, referring to disLnct appearance differences for males and females of the same species.
22
When not breeding, males’ basic plumage and most females’ typical coloraLon are more drab, calling less a_enLon to the birds and providing a measure of cover. Some camouflage coloraLons go further. Many birds demonstrate countershading, darker backs and lighter bellies, to diminish their cast shadows. DisrupLve coloraLon uses pa_erns and stripes to break up the outline of the bird. CrypLc coloraLons blend into the birds’ typical backgrounds, and may change with seasons, such as a fall molt to white feathers in regions of regular winter snow. All these evoluLonary strategies make a bird harder for its predators to see. Juveniles are usually crypLcally colored for protecLon. Most young songbirds get their adult or definiLve (basic or alternate) plumage at the age of one year. Some young, such as eagles, develop their adult plumage in stages over a few years. Other feather care acLviLes include water and dust baths. In shallow water, birds will fluff their feathers and vigorously flap their wings to splash water through to their skin. Some species fluff and spread their wings in the rain. Swios and swallows dip into water while flying. For a dust bath, birds will scrape a slight depression on the ground and wallow to toss dirt over their feathers. They work the dust into the feathers then shake it out. Preening follows water and dust baths. Birds may also be seen sunbathing with spread wings. These acLviLes may help control parasites.
Measuring primary feather length of an Acadian Flycatcher during banding, Great Smoky Mountains InsLtute at Tremont (Margie Hunter)
23
III. Bird Habitat
Field, Forest, and Edge
Habitat selec5on Why do certain species prefer parLcular habitats, and what influences that preference? What cues prompt a bird to select a given site? Even though birds could fly anywhere for food or breeding, they select very specific habitats. Requirements for selecLon may include readily available food sources, favorable microclimate, appropriate nesLng sites, sufficient cover, and good perch sites. Through close observaLon of species’ habitat selecLon and use, both amateur naturalists and ornithologists have significantly broadened understanding.
Habitat defined A habitat is the specific ecological condiLons of an environment in which a species lives. Various birds’ ranges may coincide, but they will ooen exploit different habitat types within that range. Large habitats usually feature subtle subdivisions or microhabitats reflecLng small shios in site characterisLcs. Birds appearing to ‘share’ a habitat may be using different microhabitats within the larger area. Unless favorable sites are limited, birds that migrate typically sLck to similar habitat types from their breeding sites to their wintering grounds. Site limitaLon forces use of different habitats. There are species, however, that seek different habitats at certain Lmes of the year based on their seasonal needs. For example, non-‐breeding habitats do not have to accommodate special requirements associated with nesLng. Habitats are selected based on their availability and potenLal to saLsfy basic survival and/or breeding needs. Habitats are not staLc, and changes in the environment may result in changes to a bird’s distribuLon. Seasonal changes to breeding habitats are a primary moLvaLon behind migraLon. Over Lme, natural processes like succession turn open fields into closed forests. As grasslands disappear, species like Eastern Meadowlark and Grasshopper Sparrow give way to woodland species, including Brown Thrasher and Yellow-‐breasted Chat. Changes introduced by humans, from habitat loss and fragmentaLon to landscape planLngs influence bird distribuLons. Northern Mockingbird, Northern Cardinal, Tuoed Titmouse, and others have expanded their winter ranges northward due to the increased use of backyard bird feeders and planLng of ornamental, winter-‐berrying shrubs. Human acLviLes have changed natural habitats and created new ones through agriculture and development. Species such as American Robin, American Goldfinch, hummingbirds, and Eastern Bluebird thrive in human environments. Peregrine Falcons can be found nesLng on the window ledges of skyscrapers. Trends in agriculture toward large-‐scale monoculture and increased pesLcide/herbicide use hurt species that might otherwise do well on such lands. Habitats may be broadly general in scale or narrowly specific. Their descripLons are based on vegetaLon and focus on the structure (general physiognomy) as well as the presence and abundance of key plant species. Plant community distribuLon represents the combined
24
influence of geology, geography, soil, hydrology, and climate (temperature and precipitaLon). As these factors change, community types and habitat boundaries shio, ooen blending from one to another creaLng intermediate ecotones. These areas of transiLon, or edge habitats, provide unique environments for a wider range of species. Eastern North American forest composiLon features mainly broad-‐leaved, deciduous trees. Species of trees vary with rainfall, temperature, soil moisture, soil composiLon, topography, aspect, elevaLon, and history of glaciaLon. Several primary habitat types have been idenLfied in eastern forests.
Primary terrestrial habitat types Boreal forest remnants (spruce-‐fir) along the spine of the Southern Appalachians accommodate species that typically breed much further north. Winter Wrens and a few Yellow-‐bellied Sapsuckers simply move up the mountainside to forests over 3,500 feet in elevaLon for breeding. Winter Wrens return to lower elevaLons in winter as do the sapsuckers, who are joined by their northern-‐breeding kin. The cooler climate of northern hardwood forests (Yellow Birch, Striped Maple, Eastern Hemlock, Yellow Buckeye) means seasonal food availability, and many birds are summer residents migraLng south in winter. This forest type is found on the Cumberland Plateau and in the Blue Ridge Mountains a_racLng Blue-‐headed Vireo, Black-‐throated Green Warbler, and Veery. Mixed deciduous forests (oak, hickory, maple, beech) found throughout the state at lower elevaLons offer nesLng habitat for year-‐round and summer residents and serve as stopovers for migraLng species. A few of the many species include Blue Jay, Ovenbird, American Redstart, White-‐breasted Nuthatch, Red-‐eyed Vireo, and Summer Tanager. Richly wooded riparian corridors follow river and stream courses and provide criLcal bird habitat, especially in drier areas. Bird migraLon pathways ooen follow these corridors. Belted Kingfisher and Bank Swallow nest in burrows along riverbanks. Meadows, pastures, and open fields a_ract grassland and edge-‐loving species like Eastern Bluebird, Red-‐winged Blackbird, Killdeer, Dickcissel, and Prairie Warbler.
Bird communi5es and compe55on Within a parLcular habitat, species may restrict their acLviLes to certain preferred parts of that habitat. In forests, Ovenbirds forage on the ground while Black-‐and-‐White Warblers glean insects from tree branches. These differing preferences can extend to sexes of a species. Female Red-‐eyed Vireos forage near their nest height, and males forage from their song perches higher in the canopy. This division of similar habitats is called resource parLLoning. Birds that eat the same type of foods can exploit different parts of the habitat without much overlap. Another way to share a habitat without compeLLon may be expressed in anatomical variaLons. Differences in beak size and shape limit the range of food sources for any given species. Birds may also Lme their arrival in a habitat to avoid direct compeLLon or enjoy a broader habitat range unLl larger or superior compeLtors arrive thus reducing the effecLve size
25
of the first birds’ territory. Birds can be adaptable, iniLaLng changes in their habitat preferences if condiLons, such as drought, warrant.
White-‐eyed Vireo is a bird of wood edges, brush, brambles, and dense undergrowth. (Margie Hunter)
Water
Ponds, lakes, wetlands, and river systems provide crucial habitat for many bird species, but especially those whose life histories and food sources are Led to water. Larger standing bodies of water -‐-‐ ponds, lakes, reservoirs -‐-‐ accommodate swimming and diving waterfowl such as ducks, geese, loons, grebes, gulls, and terns as they migrate. Several duck species winter in Tennessee, and a few, e.g., Mallard, Wood Duck, Hooded Merganser, are year-‐round residents in part to all of the state, feeding on aquaLc plants and invertebrates. Shorelines of both lenLc and loLc aquaLc systems, including marshy wetlands, provide habitat for wading birds who probe the mud and sand for aquaLc invertebrates, small amphibians, and li_oral zone plants. Shorebird-‐type species include coots, gallinules, rails, plovers, sandpipers, cranes, bi_erns, herons, and egrets. Bird species that depend on fishes or frogs for a significant part of their diet, will nest near rivers, streams, and other bodies of water. Eagles, herons, and kingfishers are primarily piscivores.
26
Many passerines, including songbirds such as warblers and sparrows, favor swamps and riparian habitats. The Louisiana Waterthrush demonstrates a parLcular preference for fast-‐flowing streams. Wetlands support richly abundant and diverse biological communiLes. A large number of naLonally rare and endangered bird species depend on wetlands as their primary habitat. In Tennessee, more than 90 percent of the historic wetlands are gone, most drained for agriculture or development. Rivers were ooen channelized to improve drainage, removing associated wetlands and wooded riparian corridors. Recent efforts to reverse these condiLons have been a boon to migratory and breeding birds in the state.
Ecological Niches and Func5ons
Insect control Just as mycorrhizal fungi engage in symbioLc relaLonships with roots of forest trees providing increased access to important nutrients, birds may offer trees an equally criLcal benefit -‐-‐ reducLon of insect herbivory. Studies have shown that trees without insect-‐eaLng birds lose twice the leaf biomass to predaLon during the year from caterpillars and other invertebrates. The deleterious effect spills into the next year when the same trees produce a third less biomass due to low food stores from reduced photosynthesis the previous year. The growth and health of forests are dependent on birds’ voracious appeLtes for caterpillars and other foliage-‐eaLng invertebrates. This finding surprised scienLsts who had long felt that terrestrial organisms lower on the food chain (plants) could not be helped by higher organisms (birds). For land-‐based organisms, the most important controls come from below, not above. It was believed that topdown control, or a trophic cascade, could only be found in aquaLc environments. Birds proved this wrong. Since then, other terrestrial trophic cascades have been idenLfied including another benefit to forest trees from the control of browsers by wolves. (Source: “Why Trees Need Birds,” Sharon Begley, NaConal Wildlife, Aug. 1, 1995, pp. 54-‐56)
Pollina5on Some flowering plants produce sweet nectar as a lure for hummingbirds. Hovering flight, long beaks, and specially adapted tongues allow these birds to probe deep into brightly colored (ooen red) trumpet-‐shaped flowers and reach the nectaries. In doing so, the birds pick up a dusLng of pollen on their foreheads which can be transferred to the sLgma of another flower. These flowers ooen have li_le or no landing plaxorm for bu_erflies, no fragrance, and nectaries too deep for long-‐tongued bees. However, their co-‐evolved partner hummingbirds have no difficulty finding and securing this energy-‐rich food source while assisLng cross pollinaLon for the plants.
27
Eastern Phoebe parent with an insect for its young (Margie Hunter)
Seed distribu5on Plants have evolved with many animal partners to exchange food for seed distribuLon. They put valuable energy and resources into the producLon of ample seeds and fleshy fruits. Nuts and seeds contain nutriLous endosperm, energy stores to assist germinaLng seedlings. Animals, including birds, relish that nutriLous energy as well, moving the seeds some distance from the parent plant, where they may be dropped or cached and forgo_en. While many nuts and seeds are eaten, enough survive in their new locaLons to perpetuate the species. The evoluLon of fleshy fruits seems to have no other raLonale than to a_ract hungry birds and other animals. Ooen seeds inside these fruits require scarificaLon -‐-‐ removal of the fleshy outer porLon and exposure of the seeds to digesLve juices in an intesLnal tract -‐-‐ to germinate. They are suitably deposited away from the parent plant with an appropriate mix of nutrients, such as nitrogen, in the animals’ feces for a healthy start in life.
Predator and prey Birds and their eggs, a nutriLous food source, are preyed upon by numerous other species in a community’s food web. Larger birds, such as hawks, falcons, and owls, eat smaller birds. Jays, crows, and ravens raid nests for eggs or nestlings. Raccoons, snakes, rats, weasels, foxes, and other animal species will seize the opportunity for an avian meal. Raptors (hawks, owls, eagles, and falcons) serve as top predators in some communiLes, consuming small mammals such as mice, shrews, squirrels, and rabbits to keep their populaLons in check.
28
Bioindicator Birds can serve as early warnings of environmental threat. Heavy use of the pesLcide DDT on forest and farm pests aoer World War II was responsible for the poisoning deaths of American Robins and other birds. DDT is persistent, accumulaLng in organisms up the food chain, from earthworms to robins. In species such as Peregrin Falcons and Bald Eagles, the chemical altered birds’ metabolism of calcium resulLng in thin-‐shelled eggs that broke during incubaLon, significantly lowering reproducLve success. Rachel Carson’s Silent Spring in 1962 chronicled these phenomena and helped inspire the modern environmental movement. More recently, the deaths of Blue Jays and American Crows tracked the spread of West Nile virus in the U.S.
Scavengers Turkey Vultures and Black Vultures serve as the cleanup crew, devouring carcasses and recycling their nutrients.
Black Vultures at work (Margie Hunter)
29
IV. Bird Iden5fica5on
AcLve birds on the move provide only brief glimpses. Grouping them based on physical similariLes and habitat helps novice birders idenLfy species quickly. Judging birds on their general shape, color pa_ern, and behavior combined with a basic knowledge of which species are found in a given region, season, and habitat, narrows the possibiliLes and improves the opportunity for successful idenLficaLon.
General Physical AppearanceShape and size A bird’s build reflects that species’ life history. Birds with similar food sources, flight styles, habitat preferences, etc., ooen have similar builds. Their silhoue_es disLnguish them from other bird groups with different life histories, giving a good impression of overall size, body shape, body proporLons, and posture, each providing clues to idenLty. Is the general shape plump and stout-‐bodied or sleek? Size may be influenced by distance or posiLon (hunkered or fluffed). Gauge it against well-‐known birds. Is it larger or smaller than a sparrow, robin, or crow? Aoer noLng overall characterisLcs, consider the shape and proporLon of individual parts. The shape and size of the beak is an important clue to the food it eats -‐-‐ thin and pointed for insect gleaning birds like warblers or short and conical for seed eaLng birds like finches. Tail shape and wing shape vary too and influence flight pa_erns. Head shape (small round, American Robin), neck length (short thick, Green Heron), body shape (small compact, warblers), tail length (long, Northern Cardinal), legs and feet (strong zygodactyl, woodpeckers) can all play a role in deducing idenLty. These characterisLcs may be judged against the bird itself or compared to other species. Beak length relaLve to head size is a good measure to disLnguish a Hairy Woodpecker (head-‐length beak) from a Downy Woodpecker (half a head’s length beak). Nuthatches have long pointed beaks compared to the short stocky beaks of similarly-‐sized chickadees.
Tonal paMern and color Note the light/dark tonal pa_ern first, then the bird’s actual colors. Feather colors can vary depending on age, wear, and breeding plumage, as well as the quality of light, and the bird may only allow a brief glimpse. Focus on simple value tones, noLng which parts of the bird appear lighter or darker. The locaLon of light or dark patches ooen separates similar species. Bright patches of color in very visible areas stand out, like the shoulder patches of Red-‐winged Blackbirds or the orange wing and tail blotches of an American Redstart. As birders become more familiar with species, the presence of white ‘flash’ feathers in the tail could indicate American Robin, Eastern Towhee, or Dark-‐eyed Junco with other easily discernible traits separaLng the three. Northern Mockingbirds ‘flash’ white in their wings as well. Northern Harriers can be disLnguished from other hawks by their white rump patch.
30
Breeding or alternate plumage of many males makes it very easy to spot and idenLfy an Indigo BunLng, Scarlet Tanager, BalLmore Oriole, American Goldfinch, or Blue Jay. Other birds downplay their differences and require a sharper eye to note finer details. SomeLmes those details are just a ma_er of degree. How bold or faint do the markings appear? Are there stronger contrasts, such as the sharply defined brown and white streaks of a female Purple Finch, or the indisLnct shades of brown streaking a female House Finch?
Small blue bird of forest canopies, Northern Parula (Margie Hunter)
Behavior Bird species exhibit unique acLons, movements, postures, and/or flight pa_erns. These disLncLve signatures, such as how it feeds, moves about, or sits, including li_le habits like tail or wing flicking, provide important informaLon. Recognizing birds by their behavior requires careful observaLon. A bird’s basic presentaLon is its posture, the pose it typically assumes. Pine Warblers crouch, holding head, body, and tail on a horizontal plane. Acadian Flycatchers sit upright and verLcal, tail poinLng down. Assess its general demeanor while sieng. Is it skiesh and nervous, placid, inquisiLve, sLff, on alert? In moLon, birds give other clues, parLcularly when feeding. Does it hop or walk on the ground? Does it move among tree branches or climb the trunk? Is it looking for flying insects or scanning foliage? Ducks feed in different ways, some diving underwater, some Lpping rumps in
31
the air (dabbling). Birds exhibit a wide range of foraging styles -‐-‐ stalking ponds, running along shorelines, plunging into water, eaLng on the wing, darLng from perches, crushing seeds, scratching in leaf li_er, or probing the ground. Flight pa_erns, e.g., flying in a straight line, bouncy up-‐and-‐down flight, gliding, riding thermals, swooping, slow or rapid flapping, etc., are ooen disLncLve enough to discern at least certain groups, if not species, with few addiLonal visual clues. Certain birds of prey can be disLnguished by the way they hold their wings (level or in a v-‐shape) when gliding. Some birds move in groups of small numbers (three or four) to large flocks of dozens or hundreds. Flocking is common in parLcular species, and other birds prefer to remain solitary. Once breeding is over and fall approaches, many species take a more relaxed approach to flocking and may even be found in mixed groups. It helps to know which birds prefer gregarious gatherings and which don’t.
Collec5ve names for birds In a group, collecLons of similar birds are ooen given a unique name, such as a ‘gaggle of geese.’ More are listed below. CollecLve names for other birds and animals can be found at this U.S. Geological Survey Web site: h_p://www.npwrc.usgs.gov/about/faqs/animals/names.htm. A wake of buzzards A parliament of owls A convocaLon of eagles A congregaLon of plovers A charm of finches An unkindness of ravens A pack of grouse A host of sparrows A ke_le of hawks A murmuraLon of starlings A scold of jays A descent of woodpeckers A rao of ducks or a paddling of ducks (when on water)
Habitat Habitat, range, and seasonality narrow the field of possible species to those most likely to be seen. This approach is termed “birding by probability.” Certain birds favor certain habitats. Learn which species frequent wetlands, forests, or fields. Sparrows with rusty heads may be Swamp Sparrow (wetlands), White-‐throated Sparrows (forests), or Song Sparrows (open, shrubby areas). Hawks may also be separated by habitat. Red-‐shouldered hawks prefer tall woods near water. Red-‐tailed Hawks like open, shrubby spaces. Cooper’s Hawks negoLate the canopies of deep woods. In addiLon, consider Lme of year (seasonality) and the birds’ geographic ranges. Hermit Thrushes are winter residents statewide in Tennessee, but in summer they either move north or are confined to the Blue Ridge Mountains from the Smokies through upper East Tennessee. Wood Thrushes, which winter in Mexico and Central America, replace Hermit Thrushes throughout Tennessee in summer. The same applies to winter resident Golden-‐crowned Kinglet and summer resident Blue-‐gray Gnatcatcher.
32
Margie Hunter (aoer Charles L. Ripper, Cornell Lab of Ornithology, and David A. Sibley, The Sibley Guide to Birds)
Field Marks Shape, color pa_ern, behavior, and habitat may only narrow possibiliLes to the general type of bird, resulLng in a choice among similar species. To arrive at a specific idenLficaLon, it is ooen necessary to carefully note individual field marks -‐-‐ disLncLve stripes or pa_erns, color patches and other physical differences delineaLng one species from another, some quite subtle. These field marks may appear on any part of the bird, and a working knowledge of basic bird anatomy is essenLal. Ornithologists have outlined the “topography of a bird,” dividing it into several main regions: beak, head, back, throat, breast, wings, tail, and legs. Several regions are subdivided further, e.g., the rump is at the base of the back; the nape is between the head and back; the belly is below the breast; the side is under the wing.
33
Image used by permission of Mr. Schmi_ and Cornell Lab of Ornithology
Head field marks: There are numerous possible disLncLons associated with the head region. • Eyebrow stripe (supercilium, stripe above the eye)• Eye-‐line (line through the eye)• Whisker mark (mustache or malar stripe, separates cheek from throat)• Throat patch• Beak color (upper and lower mandible)• Lore color (area between eye and beak’s base/nostrils)• Crown stripe (midline stripe over the head)• Eye-‐ring (ring of color around the eye)• Crest (tuo of feathers on the head)• Eye’s iris color
34
Wing field marks: Wing markings ooen remain the same whether in basic or alternate plumage. SomeLmes it is the absence of wing marks that disLnguishes a species. Certain wing markings may also appear during flight.
• Wingbars (stripes across folded wing)• Wing patches (blocks of color)• Wing lining (feathers under wing)• Primaries (long flight feathers, outer half)• Secondaries (flight feathers, inner half)• Speculum (colored secondaries of ducks)• Wing Lps
Image used by permission of Mr. Schmi_ and Cornell Lab of Ornithology
35
The red iris of Red-‐eyed Vireo may be hard to spot, but its gray crown, olive back, and black-‐bordered white eyebrow stripe help idenLfy it. (Margie Hunter)
Songs, Birding by Ear A bird does not have to be seen to be idenLfied. Its song is a unique vocal signature. Bird songs may be analyzed and characterized by certain features.
• Rhythm -‐-‐ Is the song’s tempo fast or slow?• Pitch -‐-‐ What is the bird’s vocal range, a higher pitch or lower pitch? Does the song
change pitch, rising notes or falling notes?• RepeLLon -‐-‐ Does the bird repeat sounds or phrases? How many Lmes?• Tone -‐-‐ How do the notes sound, what qualiLes to they have? Examples: clear, musical,
buzzy, scratchy, harsh, sweet, liquid, whistle, trill, flute-‐like, etc.It may be difficult to pick up all aspects at first, but song details offer important differenLaLons among species. Birds’ songs have ooen been likened to certain spoken words or phrases. These simple mnemonics offer helpful handles for idenLty. Field guides usually include these phrases.
• “Tea-‐ke_le, tea-‐ke_le, tea-‐ke_le” -‐-‐ Carolina Wren• “Drink your tea-‐e-‐e-‐e-‐e” -‐-‐ Rufous-‐sided Towhee• “Who cooks for you, who cooks for you-‐all” -‐-‐ Barred Owl• “Wheet-‐a, wheet-‐a, wheet-‐ee-‐oh” or “Wanna rent a video” -‐-‐ Hooded Warbler
36
• “Old Sam Peabody, Peabody, Peabody” -‐-‐ White-‐throated Sparrow• “Spring of the year” -‐-‐ Eastern Meadowlark
A few species even say their names. • “Bob-‐WHITE” -‐-‐ Northern Bobwhite• “Kill-‐DEER Kill-‐DEER” -‐-‐ Killdeer• “WHIP-‐poor-‐WILL” -‐-‐ Whip-‐poor-‐will• “Chick-‐a-‐dee-‐dee-‐dee” -‐-‐ Black-‐capped Chickadee• “Fee-‐BEE” -‐-‐ Eastern Pheobe• “Pee-‐o-‐weee” -‐-‐ Eastern Wood Peewee
Even when not likened to words, some bird songs are disLncLve and easy to remember. The maniacal laugh of a Pileated Woodpecker could not be confused with any other bird. The Black-‐and-‐white Warbler sounds just like a squeaky wheel turning round and round. Red-‐Eyed Vireo is someLmes called the “conversaLon bird” or “preacher bird.” Its song is a rapid fire succession of short phrases, some ascending in a quesLoning manner, lasLng a long Lme and sounding something like, “Here I am. Where are you? I am fine. How are you?” A song also reveals where to look for the bird to note physical characterisLcs and field marks. If a bird can be spo_ed while singing, the combinaLon of visual and aural impressions makes a powerful connecLon. Regional audio guides and mobile device apps to take into the field are available, the la_er pairing visual images of each species with the song.
37
V. Birds of Tennessee
Major Bird Groups
Most years TWRA issues a Field Checklist of Tennessee Birds. With few excepLons, the groupings and their order follow the presentaLon of species in most field guides. Bird groups in Tennessee are presented here by taxonomic orders, primarily following Peterson’s arrangement (2010) based on the American Ornithologists’ Union Checklist of North American Birds. The main deviaLon here is the placement of Strigiformes (owls) with Falconiformes (hawks/eagles, falcons) to discuss raptors as a group. Tennessee species key: M migrant, WR winter resident, SR summer resident, YR year-‐round resident. Most accounts include one or two commonly found species in Tennessee.
Order Anseriformes -‐-‐ Web-‐footed Waterbirds This order includes all geese, ducks, and swans in a single family, AnaLdae. As a family, these medium to very large-‐sized swimming birds are characterized by large heads, variously fla_ened bills, long necks, short tails, heavy bodies, long wings, and webbed feet. Habitats include various aquaLc landscapes such as seasonal wetlands, marshes, lakes, rivers, coastal estuaries, and ocean bays.
• Geese are large gregarious birds, heavy bodied with longer necks. They fly in formaLons and honk in flight. More terrestrial than ducks, geese eat grasses, grains, and aquaLc plants. TN: 4 WR, 1 YR, Canada Goose common
• Swans are white with long necks and eat aquaLc plants and seeds. All three species have minimal presence in the state; naLve Tundra and Trumpeter swans are occasional winter residents, Mute Swan is introduced in the northern U.S. and expanding its range.
• Dabbling ducks upend to feed on aquaLc plants and small aquaLc life and take flight directly into air. TN: 7 WR, 2 YR, Mallard common.
• Diving ducks plunge below water to feed and run across the water’s surface when taking flight. Their feet are posiLoned closer to their tails. Food sources are various forms of aquaLc life, including mollusks and crustaceans (Scoters) and fishes (Mergansers). TN: 10 WR, 4 M, 1 YR
Order Galliformes -‐-‐ Upland Game Birds These ground-‐dwelling, chicken-‐like birds form small flocks and forage insects, seeds, buds, and fruits. There are three species (two families) in Tennessee.
• New World Quail (Odontophoridae, TN: 1 YR) -‐-‐ Northern Bobwhite is a small plump bird of fields or open woodlands. PopulaLons are declining from habitat loss.
• Grouse, Turkeys (Phasianidae, TN: 2 YR) -‐-‐ Wild Turkeys are large birds; males have a red wa_le and beard on the neck and fan their tails in display. Ruffed Grouse ‘drum’ their wings to produce a characterisLc thumping sound. Both are woodland species.
38
Orders Gaviiformes and Podicipediformes -‐-‐ Swimming Birds Loons (Gaviidae, TN: 2 M, 1 WR) -‐-‐ Large and long-‐bodied, loons remain in open water when not acLvely nesLng. They dive and pursue small fishes, crustaceans, and other aquaLc life underwater with “daggerlike” bills. Common Loon is most ooen seen. Grebes (Podicipedidae, TN: 1 M, 2 WR, 1 YR) -‐-‐ Grebes built floaLng nests in marshes and dive for food. Their toes are lobed rather than webbed. Pied-‐billed Grebe is common.
Order Pelicaniformes -‐-‐ Large Waterbirds RepresenLng several families of large waterbirds, including some that are mainly seabirds, this order has three species, each in a separate family in Tennessee.
• American White Pelicans (Pelecanidae), TN 1) are huge birds with fla_ened bills and large throat pouches, eaLng mostly fishes and crustaceans. They may nest or be an occasional winter resident along the Mississippi River floodplain.
• Double-‐breasted Cormorant (Phalacrocoracidae: TN 1) is the primary inland species in this family with a slender, hook-‐Lpped bill and orangey throat pouch. It ooen stands erect with wings spread and is a summer resident, winter resident, or year-‐round resident in different parts of the state.
• Anhinga (Anhingidae, TN: 1 SR) is the only species in North America, similar to a cormorant with a longer neck and tail and a sharply pointed bill. Its summer breeding range includes the southwestern corner of the state.
Order Ciconiiformes -‐-‐ Large Wading Birds Four families of medium to large wading birds feature long legs and long, spearlike beaks. Except for vultures, habitats for all center on water in marshes, ponds, streams, swamps, moist fields, or mudflats, feeding on fishes, crustaceans, insects, amphibians, and someLmes other small animals.
• Herons, bi_erns, egrets (Arndeidae) -‐-‐ Long necks are folded into an S-‐shape in flight. TN: bi_erns (1 M, 1 SR), egrets (3 SR), herons (2 WR, 3 SR, 1 YR); Great Blue Heron is common.
• Ibises (Threskiornithidae, TN: 1 SR) -‐-‐ The White Ibis has a red face and reddish, slender, decurved bill. Its summer range clips the extreme southwest corner of the state.
• Storks (Ciconiidae, TN: 1 SR) -‐-‐ The Wood Stork has a naked (featherless) head and black flight feathers. Southern Tennessee grazes the northern edge of its breeding range.
• Vultures (CatharLdae, TN: 1 YR) -‐-‐ large black birds with naked heads; Turkey Vultures have red heads, Black Vultures have white, underwing patches. They eat carrion. Many ornithologists disdain the colloquial use of the name “buzzard” for New World vultures. The term is ooen applied to various birds of prey in Europe.
39
Orders Falconiformes and Strigiformes -‐-‐ Raptors Raptors are carnivorous birds. Mostly large and stout bodied with strong feet, their hooked talons and beaks are designed to capture live prey and tear flesh, including small mammals, fishes, smaller birds, repLles, and amphibians. Long, broad wings for soaring flight and keen eyesight facilitate their hunLng ability. Most hunt by day, but owls hunt mainly at night, locaLng prey with equally keen hearing. Their capacity for noiseless flight gives them the element of surprise, the result of a serrated ‘comb’ of sLff feathers along the wings’ leading edges, fringed trailing edges, and a soo down coaLng the wings’ upper surfaces. Found in all habitat types, raptors serve the important ecosystem funcLon of top predators in some communiLes. They regurgitate pellets composed of their prey’s undigested parts, such as bones, fur, beaks, claws, and feathers. All raptor species in Tennessee are listed.
Falconiformes -‐-‐ There are two families of diurnal raptors. The hawk group is further divided into categories based on similar characterisLcs. 1. Accipitridae (hawk group) -‐-‐ osprey, kites, eagles, harriers, accipiters, buteos,
• Osprey (SR) -‐-‐ large bird, hovers over water with feet-‐first plunge for fishes• Kites -‐-‐ falcon-‐shaped pointed wings, TN species Mississippi Kite (SR) an aerial
insecLvore • Eagles -‐-‐ large body, long wings, larger beaks; Bald Eagle (YR), Golden Eagle (WR)• Harriers -‐-‐ slim wings, long tail, in open country; Northern Harrier (WR)• Accipiters -‐-‐ long-‐tailed woodland raptors (bird hawks), short wings, agile; Sharp-‐
Shinned Hawk (YR), Cooper’s Hawk (YR)• Buteos -‐-‐ large hawk, broad wings, wide tail, high soaring in wide circles; Red-‐
shouldered (YR), Broad-‐winged (SR), Red-‐tailed (YR), and Rough-‐legged (WR) 2. Falconidae (falcon group) -‐-‐ falcons; streamlined birds with pointed wings, smaller and fast; Peregrin Falcon (YR), American Kestrel (YR), Merlin (WR)
Strigiformes -‐-‐ Two families of owls are our nocturnal raptors, characterized by large heads, flat faces forming facial disks, forward-‐facing eyes, silent flight, and the ability to turn their heads 270 degrees. 1. Tytonidae -‐-‐ Barn Owl (YR) 2. Strigidae -‐-‐ Eastern Screech (YR), Great Horned (YR), Barred (YR), Long-‐eared (WR), Short-‐eared (WR), Northern Saw-‐whet (YR) owls
40
Barred Owl (Margie Hunter)
Order Gruiformes -‐-‐ Marsh Birds• Rails, Coots, Gallinules (Rallidae) -‐-‐ Rails prefer marshes with grassy, reedy vegetaLon.
Coots and gallinules swim in more open water. Both eat aquaLc plants and animals. TN: rails (2 M, 1 SR), American Coot (WR, common), Common Gallinule or Moorhen (SR)
• Cranes (Gruidae, TN: 2 M/WR) -‐-‐ MajesLc, long-‐necked birds with a red facial patch and a tuo of feathers over the rump, cranes are omnivores found in marshes, prairies, and fields. Endangered Whooping Cranes stop through Tennessee during migraLon and can winter here, as do Sandhill Cranes.
Order Charadriiformes -‐-‐ Shorebirds Shorebirds are wading birds found predominately along shorelines. They forage in sand and mud for invertebrates and other small aquaLc fauna using thin beaks for probing. Sizes range from small to medium with varying shapes and proporLons important for idenLficaLon.
• Plovers (Charadriidea, TN: 5 M, 1 YR) -‐-‐ Plovers feature a compact build, thicker neck, and thinner beak. They run in short starts and stops. Killdeer is common.
• SLlts and Avocets (Recurvirostridae) -‐-‐ Both types are slim waders with long legs and very slender beaks, but the avocet’s beak curves upward. TN: Black-‐necked SLlt (SR); American Avocet (M); both are common.
41
• Sandpipers and Phalaropes (Scolopacidae, TN: 20 M, 1 WR, 1 YR/SR) -‐-‐ small to large shorebirds with slender beaks. Lesser Yellowlegs is common.
• Gulls and Terns (Laridae) -‐-‐ Gulls (TN: 3 M, 3 WR) are gregarious omnivores in open areas, someLmes in mixed flocks, with stout bodies and slightly hooked bills. Terns (TN: 4 M, 1 SR) are smaller, slender with straight bills, eaLng small fishes. Both groups nest colonially on the ground. Ring-‐billed Gull is common.
Order Columbiformes -‐-‐ Pigeons and Doves Pigeons and doves (Columbidae, TN: 3 YR) -‐-‐ NaLve Mourning Dove (common) and non-‐naLve Rock Pigeon and Eurasian Collared-‐Dove nod their small heads as they walk and have plump bodies and low, cooing vocalizaLons. Adapted to urban environments, they feed on seeds, fruit, and insects.
Order Cuculiformes -‐-‐ Cuckoos Cuckoos (Cuculidae, TN: 2 SR) -‐-‐ Slender birds with long tails, cuckoos have zygodactyl feet and eat insects in woodlands or edges and thickets. Yellow-‐billed Cuckoo is common.
Order Caprimulgiformes -‐-‐ Nocturnal Birds Goatsuckers (Caprimulgidae, TN: 3 SR) -‐-‐ Referred to as “Goatsuckers” or “Nightjars,” Common Nighthawk, Whip-‐poor-‐will, and Chuck-‐will’s-‐widow are insecLvores whose Lny beaks belie large bristled gapes designed to forage in flight. The first species prefers open areas and is ooen seen in urban seengs. The la_er two are less common in drier woods or bo_omland forests respecLvely. As a group, they have short legs, large eyes, and crypLc coloraLon.
Order Apodiformes -‐-‐ Hummingbirds, SwiW Hummingbirds (Trochilidae, TN: 1 SR) -‐-‐ Our smallest birds possess the ability to hover and fly backward. Their feathers are iridescent, and males have colorful throat patches. Needlelike bills are designed to sip nectar. A_racted to brightly colored flowers, parLcularly red, hummingbirds are found around more open habitats such as woodland edges and are frequent garden visitors. They also eat small insects and spiders. Ruby-‐throated Hummingbird is a common summer resident, and on rare occasions a Rufous Hummingbird may be spo_ed in winter. Peterson accurately describes them as “pugnacious.” Chimney Swio (Apodidae, SR), looks similar to a swallow with a flat skull, narrow wings, and rapid flight that alternates spurts of flapping with sailing. It eats flying insects in open habitats including ciLes.
Order Coraciiformes -‐-‐ Kingfishers Belted Kingfisher (Alcedinidae, TN: 1 YR) is fairly common and has a large, tuoed head with a thick, pointed beak. NesLng in river banks, it perches overhead and plunges into the water for fishes, its primary food.
42
Order Piciformes -‐-‐ Wood-‐boring Birds Woodpeckers and allies (Picidae, TN: 1 WR, 6 YR) -‐-‐ Chisel-‐like beaks, strong zygodactyl feet, sLff tails, and long tongues are all important adaptaLons to forage for wood-‐boring insects, or in the case of Yellow-‐bellied Sapsucker, drill rows of holes a_racLng insects to the sap. Northern Flicker may feed on ground ants. The smallest bird is the Downy Woodpecker at 6.5 inches; most are 8 to 9 inches, with Northern Flicker (12 inches) and Pileated Woodpecker (17 inches) much larger. Treed habitats can range from forests to open woodlands and backyards.
Order Passeriformes -‐-‐ Perching Birds or Passerines By far the largest order of birds in North America, there are 28 families of passerines. Tennessee hosts 23 of them. Passeriformes is divided into two suborders: Passeri or oscines, also called the songbirds, and Tyranni or suboscines. Suborder Tyranni is primarily one family, Tyrannidae, the Tyrant Flycatchers, considered the largest family of birds in the world. Unlike the oscines, which must learn their complex songs, suboscines innately know their more simple vocalizaLons. Species within the various genera ooen closely resemble each other, making idenLficaLon more challenging. Most species perch upright in trees watching for flying insects, swooping out to catch them on the wing. Flycatchers like wooded to shrubby, open habitats, and Eastern Phoebe (YR) has adapted to human-‐built structures for nesLng sites. Other TN species: 1 M, 10 SR -‐-‐ 3 restricted to East Tennessee and 2 to West Tennessee. Suborder Passeri contains the songbirds (oscines), mostly small birds ooen characterized by colorful plumage and complex vocalizaLons which must be learned.
• Shrikes (Laniidae, TN: 1 YR, western half) -‐-‐ Loggerhead Shrike perches in open habitats on shrubs or wires. A hook-‐Lpped beak helps capture and consume insects and small animals. May impale prey on thorns or barbed wire.
• Vireos (Vireonidae, TN: 6 SR, 1 M) -‐-‐ Vireos are small woodland birds with olive or gray backs, similar to but not as acLve as warblers. Their beaks are somewhat thicker with a slight hook at the Lp, eaLng insects and fruit. One group has wing bars and eye-‐rings, the other no wing bars and an eye stripe. White-‐eyed Vireo, common.
• Jays, Crows (Corvidae, TN: 4 YR) -‐-‐ All are large birds; crows and Common Raven are very large. They frequent a wide array of habitats with an equally wide range of foods. Blue Jay and American Crow are common statewide. Fish Crow is restricted to far West Tennessee and Common Raven to East Tennessee.
• Larks (Alaudidae, TN: 1 YR) -‐-‐ Larks are brown birds with long back claws, eaLng seeds and insects in open meadows and fields. Horned Lark has two small tuos of feathers on its head.
• Swallows (Hirundinidae, TN: 6 SR) -‐-‐ Slim birds with forked tails, pointed wings, short beaks, and Lny feet, swallows are graceful in flight and pursue flying insects in open country, someLmes preferring locaLons near streams or rivers. All have a white belly except Purple MarLn. The Barn Swallow has a deeply forked tail, and the Cliff Swallow’s is barely notched.
43
• Chickadees, Titmice (Paridae, TN: 3 YR) -‐-‐ Small woodland birds common at backyard feeders, chickadees and Ltmice ooen flock together. Carolina and Black-‐capped Chickadees both have black caps and throats, but the la_er is found only in the mountains. Large, dark eyes, tuoed crest, and rich gray color characterize the Tuoed Titmouse. They forage for seeds and insects.
• Nuthatches (Siedae, TN: 2 YR, 1 WR) -‐-‐ Nuthatches have strong feet and beaks and a stubby tail, foraging down tree trunks headfirst. They also eat seeds, nuts, and suet. White-‐breasted Nuthatch is the most common statewide, and though a year-‐round resident, Brown-‐headed Nuthatch is mostly found in the southern Ridge and Valley Province, preferring the open pine woods of coastal states.
• Creepers (Certhiidae, TN: 1 WR) -‐-‐ Brown Creeper is a small, speckled bird with a slender, slightly curved beak, and sLff tail. It spirals around tree trunks in woodlands probing for insects.
• Wrens (TroglodyLdae, TN: 2 M, 1 WR, 2 SR, 1 YR) -‐-‐ These small brown birds have compact bodies, cocked tails, and loads of energy. Most prefer thickets, tangles, or undergrowth, though two species are found in grassy marshes. They feed on insects and spiders. Carolina Wren is common statewide.
• Kinglets (Regulidae, TN: 2 SR) -‐-‐ Brightly-‐colored crowns and bold wing bars stand out on these Lny, acLve birds. They feed on insects in woodlands.
• Gnatcatchers (Sylviidae, TN: 1 SR) -‐-‐ The Blue-‐gray Gnatcatcher has a very long tail that is mostly white below. It forages for insects in swampy woods or riparian habitats.
• Thrushes (Turdidae, TN: 2 M, 1 WR, 2 SR, 2 YR) -‐-‐ Many thrushes are brown-‐backed, spo_ed birds, and those of other colors (Eastern Bluebird, American Robin) show their kinship in the spo_ed breasts of juveniles. They have large eyes and slender beaks, eaLng a variety of invertebrates and fruits. Most choose forest habitats, but bluebirds prefer open country. American Robins are quite versaLle in habitat.
• Mockingbirds, Thrashers (Mimidae, TN: 1 SR, 2 YR) -‐-‐ Referred to as “mimics,” Gray Catbird, Brown Thrasher, and Northern Mockingbird display extensive song repertoires delivered in succession. Brown Thrasher repeats phrases twice, Northern Mockingbirds three or more Lmes. They eat insects and fruit and like to nest in brushy thickets.
• Starlings (Sturnidae, TN: 1 YR) -‐-‐ European Starling, an introduced species now spread throughout the U.S., is considered an invasive pest species.
• Pipits (Motacillidae, TN: 1 WR) -‐-‐ American Pipit is streaked, somewhat resembling a thrush, with long back claws and a thin beak. It walks briskly, foraging seeds and insects in fields and along shorelines.
• Waxwings (Bombycillidae, TN 1 YR) -‐-‐ Cedar Waxwing is a sleek brown bird with a pointed crest, black face mask, reddish Lps on secondary wing feathers, and a yellow band across the tail Lp. It eats fruits and insects in open woodlands.
• Wood-‐warblers (Parulidae, TN: 13 M, 2 WR, 21 SR, 1 YR) Small birds with thin, sharply pointed beaks, warblers represent the largest group of any birds in Tennessee with 37 species. As a group, they are considered brightly colored; a few are disLncLvely colored. Most, however, are generally similar, requiring close examinaLon of field marks to
44
idenLfy. They eat insects and fruit. Nearly all need some sort of wooded cover (thicket to forest), and a few desire proximity to streams or wetlands. Yellow-‐rumped Warbler is a common summer resident.
• Sparrows (Emberizidae, TN: 1 M, 5 WR, 4 SR, 4 YR) -‐-‐ Sparrows have short conical bills and are small birds, typically brown and striped or spo_ed. Towhees are larger, and both they and Dark-‐eyed Juncos are only striped and spo_ed as juveniles. The family feeds on seeds, insects, and fruit seasonally. Open fields, prairies, marshes, thickets, undergrowth, or swamps are the primary habitats, but juncos prefer to nest in forests. Eastern Towhees are common year-‐round residents.
• Northern Cardinal, Tanagers, Grosbeaks, BunLngs (Cardinalidae, TN: 1 M, 6 SR, 1 YR) -‐-‐ This group features very colorful, medium-‐sized birds with stout beaks designed primarily for eaLng seeds, though they forage on fruit and insects too. Forests, woodland edges, or brushy thickets and riparian corridors saLsfy all but the Dickcissel, which prefers fields and prairies.
• Blackbirds (Icteridae, TN: 1 M, 3 WR, 2 SR, 4 YR) Medium to large birds, this group also includes the brightly colored orioles. All but the Bobolink have sharp beaks. They eat a variety of foods including seeds, insects, fruits, and small aquaLc fauna. Bobolink, meadowlarks, blackbirds, and grackles prefer more open fields. Orioles prefer woodlands, and the Brown-‐headed Cowbird parasiLzes the nests of other woodland passerines. Red-‐winged Blackbird is common.
• Finches (Fringillidae, TN: 2 WR, 3 YR) -‐-‐ The tails of finches are relaLvely short and notched. Their stout beaks crack seeds, but they also feed on insects and small fruits. All like open woods and can be found in residenLal areas, except for the Red Crossbill, whose year round range in Tennessee is confined to small areas of the Southern Appalachians. House Finch and American Goldfinch are regular visitors to backyard feeders and gardens with coneflowers.
• Old World Sparrows (Passeridae, TN: 1 YR) -‐-‐ House Sparrow was introduced from Europe in 1840 and is now found throughout the U.S. It feeds on insects and seeds around ciLes and farms.
Non-‐na5ve Species Sources differ on the number of invasive bird species in Tennessee varying from five to eight. An invasive bird is defined as any introduced species deemed “detrimental to the populaLon” of naLve birds.
• Mute Swans compete with Tundra Swans and other naLve birds for territories and nesLng habitat. Their presence has been shown to cause shorebirds such as Black Skimmer, Least Tern, Forster’s Tern, and Common Tern to abandon their nests. Mute Swans are also known to kill Mallard ducklings and Canada Goose goslings.
45
• European Starlings destroy eggs and kill nestlings of naLve cavity-‐nesLng birds such as Eastern Bluebirds, woodpeckers, flickers, Great Crested Flycatchers, Tree Swallows, and Purple MarLns.
• European House Sparrows are aggressive and destrucLve to naLve cavity-‐nesLng birds.• Rock Pigeons live mostly in urban areas, and currently, there isn’t much evidence of a
negaLve effect on naLve bird populaLons. The same is true for Eurasian Collared Dove, whose populaLons remain small and isolated.
• Muscovy Duck is usually found on ponds, lakes, and reservoirs where it can interbreed with other species producing hybrids.
• Ring-‐necked Pheasant, Chukar, and other game birds have been released for hunLng. They compete with naLve grassland birds for nesLng territory and food.
Rare Species Thirty-‐four bird species are listed in A Guide to the Rare Animals of Tennessee, March 2009, compiled by the Tennessee Department of Environment and ConservaLon’s Division of Natural Areas [March 2009]. All but five are state listed as Deemed in Need of Management, Threatened, or Endangered. Only one is federally listed as Endangered (exLncLon possible), the Interior Least Tern, found along Mississippi River sandbars and islands. Some species are rare here because Tennessee offers li_le suitable breeding habitat. The year-‐round range for Northern Saw-‐whet Owl, listed as Threatened in Tennessee, includes New England, northwestern U.S., and northern Rockies. It breeds in southern Canada. However, it also finds suitable habitat in the high elevaLon spruce-‐fir forests of the Blue Ridge Mountains. This habitat is small, patchy, and under threat itself, and the Northern Saw-‐whet Owl populaLons in Tennessee are correspondingly small and suscepLble, warranLng a state rank of S1, extremely rare, criLcally imperiled in the state, and parLcularly vulnerable to exLrpaLon. Other birds species are rapidly declining throughout their ranges, parLcularly neotropical migrants. Among the most threatened is the Cerulean Warbler. More than 90 percent of its wintering habitat in the tropical mountain forests of Columbia is gone. Efforts underway since the mid 2000s have preserved several tracts of remaining habitat and partnered with local agricultural interests to promote shade-‐grown coffee farms and reforestaLon. In Tennessee, Cerulean Warblers are found statewide in all physiographic provinces and breed in mature deciduous forests, parLcularly in floodplains or mesic condiLons. Its current status is listed Deemed in Need of Management and state ranked as S3B, breeding populaLons “rare and uncommon in the state...due to factors that make it vulnerable to exLrpaLon.” Its range in the state is considered restricted with small populaLons (ooen 80 or fewer) and recent, widespread populaLon declines. The Cerulean Warblers’ need for mature trees in relaLvely unbroken tracts must be factored into state forest management plans.
46
VI. Threats to Na5ve Birds
Development/landscape altera5on This represents the largest threat to birds. Loss of grasslands and wetlands to agriculture and other development has been extreme over the last century, eliminaLng crucial stopover and nesLng habitat for migratory and breeding birds.
Forest fragmenta5on Declines, quite steep in some instances, in songbird populaLons have been directly Led to fragmentaLon of forests. The threats of forest fragmentaLon do not come just from large-‐scale development, agriculture, or clear-‐cut Lmber pracLces. Breaks as narrow as logging roads and powerlines open the forest enough to allow increased predaLon and cowbird parasiLsm. Good forest management should consider the high value of healthy populaLons of bird species, many of which need large, unbroken expanses of forests to thrive.
Non-‐na5ve invasive plant species ExoLc invasive plants displace co-‐evolved naLve species depriving migraLng birds of valuable food resources along the migratory flyways and in their breeding habitats. Most naLve insects do not recognize non-‐naLve plants as food sources or do not have the evolved enzymes needed to digest them. Therefore, insect populaLons drop drasLcally in areas infested with non-‐naLve species. Non-‐naLve plant fruits eaten by birds are ooen of li_le nutriLonal value. Amur Bush Honeysuckle (Lonicera mackii) fruits contain carbohydrates but do not provide the high lipid (fat) content of naLve fruits, such as dogwood (Cornus) species or Spicebush (Lindera benzoin), needed to fuel the energy demands of migraLon. (h_p://www.nps.gov/plants/alien/pubs/midatlanLc/loma.htm) Heavenly Bamboo (Nandina domesCca) fruits have been found to be toxic to bird species. (“Feeding Behavior-‐related Toxicity Due to Nandina domesCca in Cedar Waxwings,” Moges Woldemeskel and Eloise L. Styer, Veterinary Medicine InternaConal, Vol. 2010, h_p://www.hindawi.com/journals/vmi/2010/818159/) Brilliant red coloraLon is a sign of male health and vigor in Northern Cardinals, yet Amur Bush Honeysuckle fruit improves the feather color of all birds, giving ‘inferior’ males an edge in a_racLng mates and reducing geneLc vitality in the species. (“Non-‐naLve Plants: Ecological Traps,” John Carey, NaConal Wildlife Magazine, Jan. 14, 2013, h_p://www.nwf.org/news-‐and-‐magazines/naLonal-‐wildlife/birds/archives/2013/ecological-‐traps.aspx) Bird species such as Northern Cardinals, Wood Thrushes, and American Robins ooen use exoLc shrubs like Bush Honeysuckle and MulLflora Rose (Rosa mulCflora) as nest sites. Research demonstrates ‘daily survival rate’ (DSR) decreases in these sites compared to naLve trees due to increased predaLon. (“Placement and Mortality: Is Nest PredaLon a Random Event in Space and Time,” Kenneth A. Schmidt and Christopher J. Whelan, The Condor, Vol. 101, No. 4, Nov. 1999, pp. 916-‐920.)
47
Pollu5on and LiMer Acid rain washes calcium from the soil negaLvely affecLng the prey birds eat. Calcium loss in their diet has an impact on egg formaLon. Environmental toxins accumulate in prey or contaminate water and nesLng sites. Excessive nutrients in water can cause rapid plant growth in aquaLc systems (eutrophicaLon) deterioraLng habitat quality. Roadside li_er a_racts rodents which in turn a_ract raptors and owls who fall vicLm to vehicular strikes.
Predators, parasites, and compe55on NaLve birds have always dealt with snakes, raccoons, crows, and other natural predators, but the introducLon of domesLc cats has had a devastaLng affect on bird populaLons. A wildlife biologist in Wisconsin esLmated rural cats kill millions of birds annually in his state, and a Washington, D.C. study showed 80 percent of fledgling Gray Catbirds died, half due to house cats. (“How to Green Your Pet,” Susan McGrath, Audubon, July /August 2014, p. 53) With the increase in forest fragmentaLon, parasiLc cowbirds have an easier Lme reaching songbird nests to lay their eggs for brooding and rearing by the passerine. Female Brown-‐headed Cowbirds usually lay one egg per nest, up to 40 eggs per season, ooen removing one egg of the host species. Some parasiLzed species recognize the strange egg and destroy it or abandon the nest, but others do not, expending Lme and energy on the baby cowbird at the expense of their own young. Despite a low success rate, the increased opportunity to reach unsuspecLng species in a fragmented forest has led to a cowbird populaLon explosion and declines in many species targeted by them. Non-‐naLve birds, such as House Sparrows and European Starlings, experience exponenLal populaLon growth at the expense of naLve species, taking over nesLng sites and food resources. As the dynamics of biological communiLes are altered, even populaLons of certain naLve species may experience dramaLc increases as well, placing stress on community environments in ways that can negaLvely affect other naLve species.
Disease Pathogens such as House Finch disease (an eye disease) and West Nile virus have hit certain species hard. Blue Jays and American Crows suffered high mortality from West Nile.
Manmade structures During the day, birds fooled by sky reflecLons in large windows and glass-‐paneled office and apartment buildings will fly into them, resulLng in a 60% mortality rate. CommunicaLon towers and wind generators are responsible for very high casualLes during night migraLon. City lights at night confuse migraLng birds navigaLng by the stars causing many to collide with manmade structures. Experts esLmate 100 million neotropical migrants die each year from these nigheme collisions. (“Collateral Damage,” Rene Ebersole, Audubon, July/August 2014, p. 15)
48
Disturbance Aircrao, recreaLon (jet skis, off-‐road vehicles), and other outdoor acLviLes disrupt nesLng, feeding, or roosLng areas.
What you can do• Keep pet cats indoors and support feral spaying/neutering programs.• Establish a backyard wildlife habitat.• Landscape with naLve plants providing a variety of fruit and seed types.• Set out seed or nectar feeders, suet, peanuts, or fruit, especially in winter.• Set out a clean, shallow water source for bathing, drinking.• Put up nest boxes and clean them at least annually.• ParLcipate in annual bird counts and assist bird banding projects.• Drink only shade-‐grown coffee.• Support reforestaLon efforts and roadless wilderness areas.• Support conservaLon efforts in key wintering and breeding grounds.• Support local “Light’s Out” efforts (sponsored by Audubon) to turn off building lights
during migraLon.• Support local, state, and federal clean water and air regulaLons.• Do not use pesLcides.• Cover large reflecLve windows to prevent bird strikes. Hang neeng or moving objects in
front, break up reflecLons with sLckers or soap streaks, shade windows with trees or an awning. Construct new window openings with a downward Llt to reflect ground not sky.
Kathy Shaw and Tennessee Naturalist Cyndi Routledge assist duck banding at Tennessee NaLonal Wildlife Refuge. (Sandy Bivens)
49
VII. Birding Ac5vi5es
Bird Counts and Bird Banding The growing field of CiLzen Science allows and encourages the general public to engage in “the collecLon and analysis of data relaLng to the natural world...as part of a collaboraLve project with professional scienLsts.” Public parLcipaLon in scienLfic research (PPSR) provides a way for each person to help protect natural resources in the face of environmental problems ranging from overdevelopment to climate change. Tennessee Naturalists may parLcipate in annual bird counts, assist with several established bird banding programs in the state, or contribute to other online data-‐gathering programs. h_p://www.birds.cornell.edu/citscitoolkit
Bird counts Considered the “longest-‐running CiLzen Science survey in the world,” the Audubon Christmas Bird Count began at the turn of the TwenLeth Century out of concern for declining bird populaLons. In response to tradiLonal game hunts held during the season, the Audubon Society proposed to count birds rather than kill them. Such long-‐term data provide a clear picture of the health and status of bird populaLons, showing general trends and pinpoinLng species in need of conservaLon protecLon. The count period runs from December 14 to January 5 each year. h_p://birds.audubon.org/christmas-‐bird-‐count Great Backyard Bird Count (GBBC) was launched in 1998 by the Cornell Lab of Ornithology and NaLonal Audubon Society as “the first online ciLzen-‐science project to collect data on wild birds and to display the results in real Lme.” Joined by Bird Studies Canada, GBBC lasts four days in mid-‐February, providing a species and number tally from at least fioeen minutes of observaLon on one or more of the days. Data are submi_ed from all over the world. h_p://gbbc.birdcount.org/ Tennessee Ornithological Society (TOS) has ten chapters parLcipaLng in a variety of events including the annual autumn hawk count, spring and fall bird counts, winter raptor survey, and annual Christmas count. h_p://www.tnbirds.org/
Other online repor5ng tools eBird -‐-‐ A joint project of Cornell Lab of Ornithology and NaLonal Audubon Society, eBird “provides rich data sources for basic informaLon on bird abundance and distribuLon at a variety of spaLal and temporal scales.” This growing online tool helps birders keep track of their own bird-‐sighLng lists and contribute their data for use in science and conservaLon. h_p://ebird.org/content/ebird/ Cornell Lab of Ornithology sponsors three other online reporLng sites for backyard birders and PPSR.
• Project Feeder Watch, a winter-‐long survey of birds visiLng feeders from November to April to track distribuLon and abundance of winter bird populaLons.
h_p://feederwatch.org
50
• Project Nest Watch, tracks the status and trends in birds’ reproducLon (nesLng Lming, number of eggs laid and hatched, number of hatchlings to survive) and how that might be affected by habitat loss, urbanizaLon, climate change, and non-‐naLve species. h_p://nestwatch.org
• Celebrate Urban Birds, founded in 2007, gains knowledge of the affect different urban environments have on birds and their locaLons, while engaging a more diverse parLcipant base in scienLfic studies. h_p://celebrateurbanbirds.org
Banding a Carolina Wren, Great Smoky Mountains InsLtute at Tremont (Margie Hunter)
Bird banding Both precise science and delicate art, bird banding requires extensive training to learn proper handling of the birds and procedural protocol, including a sLnt as apprenLce to a permi_ed Master Bander. U.S. Geological Survey and Canadian Wildlife Services coordinate with each other on the North American Banding Program issuing permits, distribuLng materials, and managing data collecLon in their respecLve countries. All U.S. acLviLes funnel through the Bird Banding Laboratory (BBL) in Laurel, MD. Banding protocols and trapping methods vary with different bird groups -‐-‐ woodland birds, water birds, raptors, flocks, hummingbirds, etc. -‐-‐ and each requires training and special permieng. Monitoring Avian ProducLvity and Survivorship Program (MAPS) through the InsLtute for Bird PopulaLons is another banding effort targeLng land birds with “constant-‐effort” mist neeng staLons. Their techniques are specifically designed
51
to produce data that monitor the effecLveness of bird conservaLon efforts. They work in cooperaLon with BBL.
Data gathered during bird banding aid important research into the life histories of species as well as provide informaLon on the health and status of populaLons, revealing trends that can influence decisions regarding habitat management pracLces or human cultural acLviLes to reduce associated negaLve effects and improve condiLons.
• species’ movements – migraLon, wintering grounds, separate populaLons• populaLon demographics – esLmates of offspring producLon and survival rates • management of game birds – esLmaLng harvests, modificaLon of hunLng regulaLons,
measure vulnerability based on age, sex, species • ecology – molt pa_erns and strategies, parasites, esLmates of territory size and
importance • monitoring endangered or threatened species
Public educaLon is an important side benefit. Many bird banding staLons are located in areas where the public can observe the acLviLes, learn about the science of birds, and become more personally engaged with birds in their area. Banding sessions occur during a specific period of Lme at various intervals, e.g., daily, weekly. Traps or nets are checked every 20 to 30 minutes; a caught bird is carefully extracted and placed in a holding bag for transport to the banding staLon. There are specific holding techniques, one called the “bander’s grip,” to minimize the potenLal for harm or stress to the bird. Aoer posiLve idenLficaLon, a Lny, individually numbered metal band is placed on the bird’s right leg. Before its release, other data are collected.
• sex, age, and weight • measurements of certain parts, e.g., wing chord length (wrist to primary feather Lp),
tarsus, bill’s length/depth/width, tail• body fat assessment
All informaLon is recorded on a field sheet and later entered online to the Bird Banding Laboratory. The enLre process takes an experienced bander about three minutes, and the bird’s health and welfare are paramount. Any bird in distress is automaLcally released. In Tennessee, bird banding staLons can be found throughout the state. A few have been operaLng for many years including Warner Parks (Nashville), Seven Islands State Birding Park (Knoxville), Whigg Meadow (Cherokee NaLonal Forest), and Big Bald Banding StaLon (Li_le Bald Mountain, Unicoi Co.) which is also the site of Southern Appalachian Raptor Research’s (SARR) banding program. Tennessee Wildlife Resources Agency has several banding programs for game species, and officials with the state’s NaLonal Wildlife Refuges band many bird types. There are three bird banding associaLons for individuals. Tennessee is part of the Inland Bird Banding AssociaLon and has eight members. Southern Appalachian Raptor Research -‐-‐ h_p://bigbaldbanding.org/big-‐bald-‐banding-‐staLon/Warner Parks -‐-‐ h_p://www.tnbirds.org/IBA/SitePages/WarnerParks.htmWhigg Meadow -‐-‐ h_p://www.tnbirds.org/IBA/SitePages/CherokeeNF-‐south.htmSeven Islands State Birding Park -‐-‐ h_p://tnstateparks.com/parks/acLviLes/seven-‐islands-‐hiking
52
Bird Watching Bird watching can be done anywhere, from a front porch to the rainforests of South America. A few general guidelines will assist beginners.
• Acquire a good field guide and become familiar with its layout• Purchase a pair of binoculars (details below)• Become acquainted with the birds expected in your area to narrow choices when
scanning bird guides• Consult the Tennessee Watchable Wildlife birds Web page for great informaLon on birds
of Tennessee -‐-‐ h_p://www.tnwatchablewildlife.org/birds.cfm• Learn where certain species are likely to be found, their preferred habitats such as
grasslands, woodlands, etc.• Join a birding group, the Tennessee Ornithological Society or a local Audubon chapter,
and a_end birding field trips• Look for bird programs offered at municipal nature centers and state parks• A_ract birds to your property; see Backyard Habitats secLon below• Read about birds -‐-‐ Bird Watcher’s Digest, Birding magazine, Cornell Lab of Ornithology
All About Birds• Reach out to more experienced birders and ask quesLons
Tennessee Naturalists watching birds at Owl’s Hill Nature Sanctuary (Margie Hunter)
53
Binoculars and scopes Prices of binoculars and scopes vary greatly and choices number in the thousands. Here are some important consideraLons.
• Cost -‐-‐ Prices range from $20 to $3,000. Expensive does not always mean best, but choosing the best binoculars for your budget will pay off in the long run.
• Size classificaLon -‐-‐ Binoculars are classified by their magnificaLon power and objecLve lens diameter (or aperture) in a pair of numbers, such as 7x42, 8x30, 10x40, etc.
• MagnificaLon -‐-‐ The first number references the magnificaLon power indicaLng how much the object is enlarged. For a 7x binocular, the image will appear seven Lmes closer than the naked eye’s view. Most will find 7x to 8x sufficient; 10x requires a steady hand to prevent image shake, affecLng ability to discern detail; 12x will likely require a tripod. Higher power also diminishes brightness.
• ObjecLve lens diameter -‐-‐ The second number refers to the diameter of the front lenses and determines light gathering capability. Larger lenses allow more light to enter, providing brighter images in dim light. A binocular’s overall size is proporLonal to its objecLve lens size. Ranging from 20mm (compact) to 50mm (full size), most popular birding binoculars are 32-‐44mm.
• Field of view -‐-‐ The width of the area visible through the lenses is expressed in angular degrees or linear feet at 1,000 yards. It can be narrow or wide, based on internal components of length, configuraLon, and design. An 8x42 binocular typically has a field of view of 340 feet at 1,000 yards or 6.5 angular degrees.
• Glass quality -‐-‐ Image quality is directly Led to glass quality. Standard grades provide good images in ideal lighLng. High-‐grade glass, such as extra-‐low dispersion glass (ED), fluoride glass (FD), and high-‐definiLon glass (HD), provide superior resoluLon and color, parLcularly in low light situaLons.
• Lens coaLngs -‐-‐ AnL-‐reflecLve coaLngs on the lenses reduce internal light loss and glare and ensure even light transmission. There are several coaLng opLons.
Coated -‐-‐ a single coaLng on at least one lens surfaceMulLcoated -‐-‐ mulLple coaLngs on at least one lens surface Full-‐coated -‐-‐ a single coaLng on all air-‐to-‐glass lens surfaces Fully mulLcoated -‐-‐ mulLple coaLngs on all air-‐to-‐glass surfaces
The last category produces light transmission of 90 to 95 percent for bright, sharp images with more contrast.
• Close focus -‐-‐ Designed for long views, binoculars require a minimum distance to bring an object into focus. Close focus allows objects at close range to be viewed, typically from three to twelve feet. This feature is useful for observing other wildlife, such as bu_erflies or amphibians. A good range for insect viewing is three to eight feet.
• Eyeglasses -‐-‐ Wearers of eyeglasses should make sure the binocular accommodates long eye relief, at least 15mm, the distance the eye can be from the binocular’s eyepiece and sLll see the enLre field of view. If the distance to your eyes is greater than the eye relief, only the center secLon of the image will be visible. Most binoculars today have ample eye relief.
54
• Size and weight -‐-‐ Binoculars come in a wide range of sizes and weights. It can be an important consideraLon when spending a day in the field. Consider arm and neck faLgue. Smaller size and weight will usually sacrifice both magnificaLon and objecLve lens diameter.
• Spoeng scopes -‐-‐ Scopes generally follow the same rules as binoculars, but usually do not focus closer than twenty feet. Take into consideraLon the addiLonal weight of a tripod and portability of the unit as a whole.
When shopping for binoculars and scopes, consult a reputable dealer with equipment in stock. There is no subsLtute for handling binoculars to find what works best. Vendors at birding fesLvals usually have equipment on display. The Wood Thrush Shop (Nashville), Wild Birds Unlimited (Memphis, Cha_anooga, Knoxville, Nashville), Bass Pro Shops, REI, and other outdoor retailers are good places to start. Eagle OpLcs, h_p://www.eagleopLcs.com, is a great online resource.
Backyard Habitats Many different animals, including numerous bird species, adapt quite well to urban and suburban residenLal areas. With a few common sense consideraLons, most backyards can be valuable habitat for birds and other creatures.
Plant a variety of na5ve plant types and sizes for sun and shade Introduce as many forest layers of verLcal straLficaLon as pracLcal including woody canopy and understory trees, shrubs, and vines plus herbaceous plants, ground covers, and grasses. Include a few evergreens as well as deciduous plants. Select flowering plants for a variety of petal colors throughout the season. Masses of bright colors in yellow, red, orange, purple, dark pink, or blue a_ract both hummingbirds and bu_erflies. Clusters of smaller flowers or flowers with large petals enable bu_erflies to land and drink more effecLvely. Avoid hybrids and double flowers which ooen have li_le or hard-‐to-‐access nectar and overhead sprinklers which can wash nectar and pollen from flowers.
Include a variety of food types Berries, fruits, nuts, and seeds along with nectar, foliage (bu_erfly larval food), and pollen are basic essenLals. Supplemental food sources from hanging feeders or plaxorms, suet, overripe fruit, sap, and manure may a_ract a wider variety of birds and other wildlife and help in winter or lean Lmes resulLng from drought, etc.
Insure a consistent supply of clean water Ponds, birdbaths, puddles, or drip and mist systems are important sources of water. Clean small containers and replace water daily to reduce mosquitos. PosiLon water sources close to vegetaLon to provide a safe perch for observaLon and retreat for protecLon. Birdbaths and
55
other drinking sources should be shallow, only a few inches deep. Backyard fish ponds or other water features should have shallow margins or easy places to perch. Birds can drown in deep water.
Provide cover for nes5ng, storms, summer heat, winter cold, and predator protec5on ProtecLve cover comes in many forms: dense shrubs or hedges, evergreens, mature trees, rock walls, brush and wood piles, vine tangles, and brambles. Shade on hot summer days is important to both birds and bu_erflies. Align vegetaLon or other structures to provide wind breaks. Where safety is not an issue, allow dead trees, snags, and hollow logs to remain. Don’t be too quick to Ldy a garden in fall. The dead foliage of meadow grasses and flowering plants ooen contain overwintering invertebrates that will feed birds and other wildlife in spring. Erect nesLng boxes for birds and bats; inverted chipped flower pots can serve as toad houses.
Eliminate use of chemical pes5cides, fer5lizers, and herbicides A diverse landscape of naLve plants will a_ract wildlife and establish a funcLoning food web to keep insect populaLons in check. Work to improve soil naturally through organic ferLlizers and compost. This approach increases soil organisms, ferLlity, Llth, and water-‐holding capacity. Plants will be healthier and be_er able to resist and withstand insect a_ack. If some arLficial means of control is necessary, use organic opLons or integrated pest management with the least toxic means.
Use cau5on when consul5ng wildlife-‐friendly plant lists Ooen these lists contain non-‐naLve invasive plants. Their palatability to wildlife is a key contributor to their invasiveness, offering ready means of wide dispersal. Overall site degradaLon, loss of naLve plant diversity, and loss of supplemental wildlife resources resulLng from the spread of invasive plants outweighs any food ‘value’ a_ributed to these species. Check these Web sites for lists of invasive plants in the region: Tennessee ExoLc Pest Plant Council, h_p://www.tneppc.org, and Southeast ExoLc Pest Plant Council, h_p://www.se-‐eppc.org.
Other considera5ons Place flat rocks in sun for bu_erfly basking. Areas of bare dirt may be used by birds for dust baths.
Cer5fied Wildlife Habitat Property meeLng these criteria can apply for cerLficaLon as wildlife habitat from the NaLonal Wildlife FederaLon. More informaLon is available at their Web site: h_p://www.nwf.org/How-‐to-‐Help/Garden-‐for-‐Wildlife/Create-‐a-‐Habitat.aspx
56
VIII. Resources
Publica5ons
Peterson Field Guide to Birds of Eastern and Central North America * Roger Tory Peterson, Houghton Mifflin Harcourt, 2010.The Sibley Guide to Birds * David Allen Sibley, Alfred A. Knopf, 2000. The Sibley Guide to Bird Life and Behavior * Chris Elphick, John B. Dunning, Jr., David Allen Sibley, Eds., Alfred A. Knopf, 2001.The Birder’s Handbook: A Field Guide to the Natural History of North American Birds * Paul R. Ehrlich, David S. Dobkin, Darryl Wheye, Fireside Simon & Schuster, 1988.Compact Guide to Tennessee Birds Michael Roedel and Gregory Kennedy, Lone Pine, 2005.Birds of Tennessee Stan Tekiela, Adventure PublicaLons, 2003Peterson Field Guide, Eastern Birds’ Nests Hal H. Harrison, Houghton Mifflin Harcourt, 1998.
Organiza5ons
Tennessee Ornithological Society -‐-‐ h_p://www.tnbirds.org/NaLonal Audubon Society -‐-‐ h_p://www.audubon.org/ h_p://www.audubon.org/chapters?state=TNNaLonal Wildlife FederaLon -‐-‐ h_p://www.nwf.org/
Internet
Cornell Lab of Ornithology All About Birds -‐-‐ h_p://www.allaboutbirds.org *About.com Birding/Wild Birds -‐-‐ h_p://birding.about.com/Tennessee’s Watchable Wildlife, Birds -‐-‐ h_p://www.tnwatchablewildlife.org/birds.cfmFernbank Science Center, Birds in the Classroom -‐-‐ h_p://fsc.fernbank.edu/birds.htmU.S. Fish & Wildlife Service Forensics Lab Feather Atlas -‐-‐ h_p://www.fws.gov/lab/featheratlas/Bird Watcher’s Digest -‐-‐ h_p://www.birdwatchersdigest.com/bwdsite/American Birding AssociaLon -‐-‐ h_p://www.aba.org/CiLzen Science Central -‐-‐ h_p://www.birds.cornell.edu/citscitoolkitUS Geological Survey Bird Banding Laboratory -‐-‐ h_p://www.pwrc.usgs.gov/bbl/InsLtute for Bird PopulaLons -‐-‐ h_p://www.birdpop.org/insLtute.htm
(* Primary source materials for much of this document.)
57
VIX. Review Ques5ons
1. Birds’ tail feathers are not used for a. stability and control in flight b. maLng displays c. balance prop on tree trunks d. lio when soaring
2. The largest species of woodpecker in Tennessee is a. Red-‐headed b. Pileated c. Red-‐bellied d. Downy
3. Bird species displaying different coloraLon for males and females exhibit a. dichotomy b. dimorphism c. diploidy d. duplicity
4. To orient themselves in the proper direcLon for migraLon, birds use a. the sun as a compass b. the stars as a compass c. the earth’s magneLc field as a compass d. all of the above
5. For the most part, nestlings of passerines (perching birds) are dependent on what major food source? a. small fleshy fruits b. seeds c. insects and other invertebrates d. small mammals and fishes
6. Frugivores eat a. fall grains b. fleshy fungi c. fleshy fruit d. flying insects
58
7. What were the key evoluLonary elements in the journey from repLles to birds? a. development of feathers and endothermy b. development of bright breeding plumage and a syrinx c. development of wings and feathers d. development of specialized nest building techniques and clasping feet
8. The feather color blue is produced by light interacLng with a. melanins b. feather structure c. porphyrins d. ceruleans
9. A bird’s syrinx a. uses a Lny fracLon of moving air to produce sound b. has three separate tracheal tubes c. can create two separate sounds simultaneously d. is only responsible for the short call notes
10. Diurnal migrants are usually a. soaring species b. insecLvores c. smallest songbirds d. night blind
11. In response to a predator sighLng, birds may emit a. flight calls b. contact calls c. alarm calls d. distress calls
12. Ground nests require a. many layers of materials for padding b. dome-‐shaped construcLon to repel water c. a high level of learned skill to properly construct d. parents to spend more Lme warming eggs
13. Females choose mates based on a. vocal abiliLes b. nest-‐building skills c. bright plumage colors d. high quality territories e. all the above
59
14. To help them break out of their shells, hatching chicks develop a. an egg tooth b. strong foot muscles c. sharp claws d. powerful wing muscles
15. The funcLon of flight feathers, the primaries and secondaries, is to provide a. flight stability b. thrust and lio c. insulaLon at high alLtudes d. rudder control
16. The largest threat to birds is a. loss of habitat b. non-‐naLve species c. parasiLc cowbirds d. aircrao
17. To get their alternate plumage, breeding males undergo a. a complete molt in winter b. a complete molt in late fall c. a parLal molt in early spring d. a parLal molt during migraLon
18. Birds preen to a. look good for their mates b. maintain feather structure and funcLon c. pull out worn feathers d. improve camouflage
19. In preparaLon for migraLon, birds will a. bulk up on fiber b. consume large quanLLes of protein c. concentrate on carbohydrates d. focus primarily on lipid-‐rich foods
20. Which of the following would not factor into bird habitat selecLon? a. good perching sites b. ample food resources c. sufficient cover d. no compeLLon
60
21. Anisodactyl refers to a. the lack of a back toe b. long skinny wings c. four toes per foot, two pairs each facing in opposite direcLons d. three toes facing forward, one backward per foot
22. Social monogamy is important for a. all bird species b. species with altricial young c. species with precocial young d. ground nesLng birds
23. Trees, insects, and birds form a trophic cascade when a. insects turn tree foliage into a food source for birds b. birds reduce insect herbivory of tree foliage c. trees a_ract insects for nesLng birds d. insects defoliate bird nest sites in trees
24. Which observaLon could help idenLfy a bird? a. feeding acLvity b. flight pa_ern c. perching posture d. all of the above e. none of the above
25. When examining bird field marks, the lore is located a. at the ‘wrist’ of the wing b. on the rump c. between the eye and the beak or nostrils d. in a ring surrounding the eye
26. An accipiter is a. an eaglet b. a hawk of the forest c. a cliff-‐dwelling falcon d. a day-‐hunLng owl
61
27. What might prompt irrupLve migraLons? a. scarce food b. severe winter c. change in day length d. both a and b e. both a and c
28. The objecLve lens diameter of binoculars determines the a. amount of light it admits b. closest distance it will focus c. eye relief d. field of view
29. Humans have influenced birds’ winter ranges through a. forest succession b. bird feeders c. ornamental fruiLng shrubs d. both b and c
30. The metabolic rate of passerines is a. equal to humans b. a third lower than humans c. 30 to 70 percent higher than humans d. two to three Lmes the rate of humans
Answer key: 1. d 2. b 3. b 4. d 5. c 6. c 7. a 8. b 9. c 10. a11. c 12. d 13. e 14. a 15. b 16. a 17. c 18. b 19. d 20. d21. d 22. b 23. b 24. d 25. c 26. b 27. d 28. a 29. d 30. c
62