Z203/ Unit 5

Ch 27: Birds (Class Aves) I. Diversity

A. Ornithology - Study of endothermic feathered tetrapods - Vertebrates with highly modified bodies for sustained flight

- Significant changes in skeletal/muscle, circulatory & respiratory systems, integument, and reproduction B. Profile

- over 9,700 species described; only fish have more species - live in all biomes; mountains to prairies, on all oceans

(North to South pole) - some live in dark caves or dive to 45 meters - bee hummingbird is one of the smallest vertebrate

endotherms (1.6 g. 2.5 inches long) - unique feather is hallmark of birds - uniformity is structure:

♦ despite evolving 150my, all are still recognized ♦ forelimbs modified as wing, though not always

functional ♦ hind-limbs adapted for walking, swimming, perching ♦ all birds have toothless horny beaks (layers of keratin) ♦ all lay eggs (oviparous) ♦ flight = driving force for uniformity

a. wings to support & propel b. respiratory system meets demands of O2

requirement & cool body c. bones lightweight but rigid airframe d. digestion & circulation meet demands of flight e. nervous system has superb sensory system

for high-velocity flight ♦ conservation of design; unlike mammals have developed far more diverse forms

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II. Origin & Relationships

A. History 1. discovery of fossil Archaeopteryx lithographica (Jurassic

aged) in 1861 linked birds & reptiles a. skull resembles modern birds but w/ teeth b. reptilian skeleton w/ clawed fingers,

abdominal ribs & long bony tail c. feather imprints along the wings

2. Zoologists had long noted similarities between birds & reptiles. Both have:

a. skulls that abut 1st vertebra w/ ball-and- socket joint (1 occipital condyle)

b. single middle ear bone (stapes) c. lower jaw composed of 4 or 6 bones d. excrete uric acid e. similar amniotic cleidoic eggs & development

3. Thomas Henry Huxley classified birds w/ therapod dinosaurs

a. group of dinosaurs w/ long, mobile S-shaped neck b. therapods belong to diapsid lineage

(archosaurians) which include crocs c. fossil evidence from Spain, China, S. America

support this link

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B. Relationships

1. modern birds include: Paleognathae (flat sternum: ostrich, kiwi, rhea, emu) Impennes (keeled: penguin) Neognathae (keeled sternum: modern birds) “New jaw” – no teeth

2. appears flightlessness evolved several separate independent times

3. larger flightless birds (ostrich & emu) became fast runners 4. flightlessness freed birds from weight restrictions (sizes

varied, many very large) III. Form & Function

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A. Feathers 1. Structure - contributes to more power & less weight - hollow quill emerges from skin follicle &

continues as a shaft or rachis - rachis bears numerous barbs - hundreds of barbs arranged in flat,

webbed surface, the vane - each barb resembles a mini-feather

♦ numerous parallel filaments or barbules spread laterally ♦ up to 600 barbules on each side of barb (may be millions in one feather) ♦ barbules overlap; they “zip” together w/ tiny

hooks (preening zips)

2. Types of Feathers - Contour feathers provide form - Flight feathers extend off wing in

flight - Down feathers under contours;

barbules lack hooks, function in insulation

- Filoplume feathers hair-like, degenerate feather w/ weak shaft & tuft or short barbs

- Powder-down feathers on herons & relatives disintegrate & release a talc-powder to waterproof

- Bristle feathers found on the head, hace a stiff rachis w/ few barbs. Used for sensory & protection

3. Origin & Development - homologous to reptile scale - develops from epidermis, nourished by

dermal core - during growth, pigments added to

epidermal cells - near end of growth, soft rachis & barbs

keratinize - when protective sheath splits apart,

feather protrudes & barbs unfold 4. Molting - full-grown feather is dead; shedding or molting cyclic - gradual (except in penguins) molting avoids bare spots - flight & tail feathers lost in pairs on each side to maintain

balance - some species, molt continuous so doesn’t impair flight - many water birds, primary feathers molted all at once &

birds grounded temporarily - most molt once a year, usually in late summer after nesting

season

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5. Color - color due to pigments or structural

reflective nature - pigments (lipochromes) color red,

orange, yellow - melanin yields black, brown, red-

brown, & gray - blue color is from scattering of light

Colors may vary between sexes (sexual dimorphism)

B.

- cavities =

- many

- total weight of feathers outweighs skeleton

skull lighter; legs heavier than als; lowers the center of gravity

round bony jamost have Kinetic skull; in some, upper jaw hinged to skull

kulls

4.

- is) is fusion of 13 vertebra w/ pelvic girdle to support legs &

(reflected light) - Skeleton 1. Bone Weight

light, delicate bones laced w/ air pneumatized (still very strong) overall reduction in number of bones (fused: tibiotarsus, carpometacarpus)

2. Skull - fused into one piece, the braincase &

orbits enlarged -

mamm 3. Jaws - horny keratinous beak molded a ws - - less kinetic than reptilian s

Vertebrae & Appendages - vertebral column rigid, most vertebra fused

except for cervical vertebra synsacrum (rear of pelv

provide rigidity for flight

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- uncinate processes interlock

- ebra,

- large Keel for

r or

present i

legs have undergone less modification; function still walking, etc. feet modified to habitat * reduced to 4 digits

C. Mu1. ached to

2. tta

&-pulley to raise wing . location of both flight muscles

ngs

the ribs & give torso strength ribs mostly fused w/ vertpectoral girdle & sternum sternum bears anchoring flight muscles (not seen in flightless birds)

- forelimbs reduced in numbefused for flight

* humerus, ulna, radius * hand reduced to 3 d gits -

-

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sclular System

pectoralis muscles attkeel, down stroke of wing supracacoracoideus muscle a ched to keel, work as a rope-

3gives them aerodynamic stability

- center weight under wi

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e- kin ts

muscle mound where tail feathers

audal vertebra)

. interwoven stringy muscles in neck give flexibility

D.

- fic prey

. 1/5th of birds feed on nectar

beaks specialized to specific foods; chisel-like woodpeckers bill has tongue extend @ head

- seed-eaters crack shell (bulky bills) - fish-eaters modified bills (serrated, scoop, spear-like)

4. main leg muscles in thigh, attach to long tendons to feet & toes

5. to loc g mechanism prevenperching birds from falling when sleeping

6. lost long reptilian tail & substitute a

rooted on pygostyle (fused c7. as many as 1000 muscles control

tail feathers for steering in flight 8

Food, Feeding, & Digestion 1. Insects Eaters

earliest birds appear to be insectivores - specialization has occurred for speci 2 Other Diets - nearly -

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- to sustain endothermy & high MR temp maintenance

- hum geon & 25x’s that of a

system: us

thrush can pass berries through tract in 30min rly developed (moistening occurs in

e buds (limited taste)

o

- tore &

hedastr

- ssist grinding in e toothless)

ble material - irrors food

- paired ceca at junction of intestine & rectum serves in fermentation (important to herbivores)

stive tract also receives products from

3. Food Quantity have voracious appetites

♦ 98% of energy budget used in mingbird uses O2 12x’s faster than pichicken

- hummingbirds eat 100% of body wt/day, blue tit eats 30% while chicken eats 3.4%

- rapid and efficient digestive♦ shrike digests a mo♦

e in 3 hours

- salivary glands are poocrop) & few tast

- long, muscular esophagusextends from pharynx tcrop crop serves to smoistens food

- crop of pigeons, doves, & parrots produce lipid & protein rich “milk” from s ding lining

- stomach (proventriculus) secretes gsome birds swallow pebbles or grit to agizzard (sinc

ic juices

- birds of prey eject pellets of undigesta(owls lack a crop)

length of small intestine mtypes (shorter in carnivores, longer in herbivores)

- cloaca at end of digegenital ducts & ureters

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E. Ciong ventricular walls & overall

a

2. n of pulmonary & systemic

3. aortic arch leads to dorsal aorta (instead of left as in mam

4. 2 jug o cont

5. unubloo to b

rate 93 beats/min b. chicken HR 250 beats/min

R 500 beats/min

7. RBC (erythrocytes) nucleated & biconvex 8. WBC & eff

repa

F. Respir1. unique design differs radically from reptiles & mammals 2. lung

♦ air (nasal/mouth → pharynx →

♦

rculatory System 1. 4-chambered heart w/ str

sizes is slightly larger in comparison to body mass (0.2%)

(chicken heart vs. hum

share complete separation)

circulations w/ mammals right

mals) ular veins have cross shunts tinue circulation as head rotates sually large arteries deliver lots of d reast & wings

6. fast heartbeat inversely proportional to size

a. turkey heart

c. chickadee Hd. humming bird HR over 1000 beats/min humans average 70 beats/min

mobile (phagocytes) active ir & immunity

icient in wound

atory System

s modified for one-way air flow & air storage: enters typical pathway

trachea → bronchi) air bypasses lungs via bronchi

& flows directly to posterior air sacs on inspiration

located through the lung

♦ng bones

♦ on expiration, air flows through lungs providing continuous air flow

♦ takes two cycles for single breath of air to pass rough the system

♦ most efficient respiratory system of any vertebrate

3. air sac system helps cool bird when

up to 27x’s more heat is produced 4. non-respiratory air sacs located in

bones, legs & wings gives buoyancy & reduce overall weight of bird

♦ finest branches off of bronchi are tube-like Parabronchi

air sacs extend into thorax, abdomen & even lo

a

th

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G.1.

pattern of glomerular filtrawatereabsorption (like mammals)

3. urinecloac

4. Uric ♦ u

♦ nitrogenous waste is harmless w/in cleidoic amniotic

♦ s♦ e♦ kidney less efficient than mammals in removing ions

(loops of Henle shorter) concentrate solutes almost equal to or slightly

mals concentrate 4-25x’s)

to ingesting salty foods &

ult

H.

1. brum, cerebellum, & midbrain tectum

nter

3. ed into

4. re size related

Excretory System pair of large metanephric kidneys composed of thousands of nephrons located in lobules

2. vertebrate tion, loops of Henle for r/salt balance & selective

flows through ureters to a acid:

se reptilian adaptation of uric acid

eggs ince low solubility, far less H2O for exxcess water absorbed in cloaca

of sodium, etc

cretion

higher than blood (mam♦ marine birds excrete larger salt

loads duesalt-H2O salt glands located above eye & end in nostrils res in “runny nose”

Nervous & Sensory Systems well-developed cere

2. chief coordinating ce(cerebral cortex) thin,

unfissured & poorly developed core of cerebrum enlargprincipal integrating center cerebral hemispheto bird intelligence

5. cere quilibrium sense & visua

6. optic bulge each side of midbrain & forms visual asso

7. sense of smell poorly developed except in flightless birds, duck

8. good hearing & superb vision; best in animal kingdom 9. ear s

ext leads

mid

inner ear

ows hearing in same

ability

sity ls used for orientation and balance

atively large for

s

♦ light-sensitive retina w/ rods & cones

e eyes forward for depth Perception

bellum houses proprioception, el cues assembled

ciation apparatus

s, & vultures

imilar to mammals ♦ no external ear flaps (pinna) ♦ ernal canal hidden in auricular feathers & to eardrum ♦ dle ear contains rod-like bone (columella) that transmits vibrations to ♦ inner ear has short cochlea, all range as humans ♦ can’t hear high frequency like

us but surpass us in to distinguish differences in pitch & inten♦ semicircular cana

10. eye similar to mammal eye but rel body size

♦ eye less spherical & almost immobile; bird turnhead instead of eye

♦ diurnal have more cones; nocturnal more rods

♦ herbivores have lateral eye placement to detect predators quicker

♦ birds of prey hav

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e to rov e sh rp monocular & binocular vision

♦ hawk eye has 8x’s the visual acuity (see a rodent over a km away)

wl’s nocturnal vision 10x’s that of

ee flower nectar guides & urine s from rodents)

I. Flight

1. Histo- exploited

to seek ts

nd-up” based on running birds w/ ive wings to snare insects

own” based on tree-climbing, leapparachuting, gliding, & finally powered flight

robably for

- t

- msion (thrust)

urface re from top,

♦ many birds have 2 fovea p id a

♦ o humans ♦ many birds see partially into UV spectrum (s

trail

ry habitat of flying insects

- provided quick escape from predators & ability better environmen

- 2 hypothesis to origin: a. “grou

primitb. “tree-d ing,

- feathers preceeded flight & arose pthermoregulation hree requirements for flight:

a. Lift b. Thrust

c. Drag

2. Wings provide Lift & create Thrust odified hand bones w/ primary feathers

providing propul- wing shape (medial part of wing & secondary

feathers) provide lift - wing streamlined w/ concave lower surface &

convex upper s- 2/3 of lift comes from negative pressu

airstream flowing longer distance overconvex surface

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- as speed decreases, lift ↑ by ↑ angle of attack, & ↑ drag a po

become too steep & stalling occurs g

. Flapping Flight = provides Thrust t

th ust tips & lift by secondaries troke

steep angle of attack

- powered stroke essential for hovering & fast, steep take-offs

. Win (aspect ratio: length to width)

Elliptical Wings (low-aspect ratio) ♦ maneuvering in forest habitats ♦ slotted between primaries to prevent stalling at

low speeds ♦ chickadee can change course 0.03 sec

long migrations

- lift-to-drag ratio determined by angle of tilt & airspeed

- t a int near 15o, angle of attack

- stalling delayed or prevented by winslots at leading edge to direct rapidly moving air across top

♦ in some, alula on the “thumb” provides midwing slot ♦ slotting provides wing-tip slots

3- requires vertical lift & horizontal thrus- r provided by primaries at wing - greatest power provided by downs- primary feathers bent upward & twist to- upstroke, primaries bend to provide thrust

4 g Forms – reflect type of flight -

- High-Speed Wings (high-aspect ratio) ♦ birds that feed on the wing or make ♦ wings sweep back & taper to slender tip, reduces

“tip vortex” turbulence ♦ flat in section & lack wing-tip slotting

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- Soaring Wis have long, narrow wings

ed,

of any design,

♦ exp of different velocities

- High-Lift Wings avy loads have wings

ed

IV.

A.

rn wintering grounds & northern ele

bundance of insects & avoid bird predators

year prevents - e

s, avoiding climatic

. M - most follow established N-S routes

- distance dependent on species and habitat requirements

ngs ♦ pelagic bird ♦ high-aspect ratio, lack wing slots & allow high spe

high lift & dynamic soaring ♦ highest aerodynamic efficiency

but less maneuverable loit highly reliable sea winds & air currents

♦ birds of prey that carry hew/ slotting, alula, & pronounced camber

♦ produce high lift at slow spe ♦ many are land soarers; broad, slotted wings

ng allow sensitive response for static soari

Migration and Navigation Migration - almost half of bird species migrate - move between southe summer breeding grounds (latitude or- exploit seasonal changes in a

vational)

- appearing one time abuildup of specialized predators xpands living space & ↓ aggressive territorial behavior

- favor homeostasiextremes & food shortages

B igration Routes

- may use different seasonal routes - journeys vary from short to long (60

days)

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rs

- A winter for total 18,000km (11,200mi)

ituitary =

- p ormones that set in motion the & care of

F in - experiment suggest vision chief aid

follow ogh ion

imuth orientation day &

♦ use the sun as a compass (determined using

ar as an axis at night

- small species migrate at night, feed by day; othe are daytime migrants - follow landmarks & other aids to navigate

rctic tern circles N. America to Europe & Africa to

C. Migration Stimulus

- long day length stimulates anterior p development of gonads & fat accumulation

ituitary releases hsequence of migration, courtship, reproduction, young

D. ind g Directions

- recognize landmarks & follow familiar routes; may lder birds

- hi ly accurate innate sense of time & direct - experiment suggest incorporate magnetic fields too

- Sun-az ♦ orientation cages show birds use sun at

stars at night

Planetariums) ♦ suggest North St - migration involves combo of environmental & innate

cues

mistakes; only best navigators leave young

V. So production

nest & rear young

- natural selection culls individuals that make

cial Behavior & ReA. Cooperative Behavior - sea birds gather in huge colonies to - land birds prefer isolation - congregate for migration & sometimes feeding

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- advantages to flocking: from enemies

aying uddling for protection against low temp

ring breeding

reproductive of “breeding season”

ence, enlarge 300x’s w/ approac)

le g involves “cloacal kiss”

vary & oviduct degenerate)

oviduct - shell membrane, shell & shell pigments secreted by lower aspects of oviduct & uterus - fertilization must take place in upper oviduct, prior to membranes & shell development

ive in oviduct for many days to weeks

♦ mutual protection ♦ greater ease in finding mates ♦ less opportunity for migration str ♦ mass h - pelicans organize coop feeding behaviors

- social interactions most noticeable du B. Reproductive System - most bird species have non-functional organs outside MALES: - testes recrud h of

breeding season (shrink to pea size - sperm stored in enlarged seminal vesic - most males lack a penis; matin - minimizes weight outside of breeding FEMALES: - most have only the left ovary & oviduct developed (right o - expand end of oviduct, infundibulum, receives the discharged eggs - special glands add albumin (egg white) to egg as pass down - sperm remain al after single mating

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species are monogamous, one

mous species

like mammals)

announce territory

success to support one nesting female

ion intense & choose dominant male D. Nesting & Care of Young

- a month incubation

- oos & cowbirds) lay eggs in

- al birds are able to feed & run/swim after being hatched Altricial birds are naked & helpless at birth, must be fed in nest week or more Nesting success in altricial species low; 20% of nests produce viable young

ilure include predators, parasites, & other

C. Mating Systems - over 90% of bird

mate per breeding season - few species “partner for life” - small number of polyga - high rate of monogamy drove high degree of

parental care ( - female enforces monogamy be selecting male - bird territories: ♦ males sing to defend & ♦ female select male based on best reproductive ♦ territory large enough

- polygyny ♦ m/c form of polygamy (1M + several F) ♦ male grouse collect on leks to display to females ♦ no male parental care

♦ competit

- nearly all birds lay eggs that must be incubated require 2week to over

- may be laid in nest (open or cavity) or on bare ground Brood parasites (cuckother’s nest Precoci

-

-

- cause of nest fafactors

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VI. Bird Popula A. Factors

/

- more thdodo bi

- causes- recent global declines in songbirds:

ss of tropical forests 250 migrants of wintering homes)

rly prepares them migrati

order Procellariformes order Musophagiformes order Pelicaniformes order Cuculiformes order Ciconiiformes order Strigiformes order Anseriformes order Apodiformes order Falconiformes order Coliiformes order Caprimulgiformes order Galiiformes order Trogoniformes order Coraciiformes order Piciformes order Passeriformes

tions

- populations vary in size from year to year - predators may cycle with prey supply (snowy owl vary w

rodents they eat) - when food supply crash, birds move - humans have aided in dispersal:

European starlings House sparrow Rock Pigeon an 80 bird species gone extinct since the 1695 rd tinction ex of extinction: habitat destruction & hunting

♦ agricultural practices ♦ forest fragmentation ♦ house cat predation ♦ lo (deprives♦ stress in wintering ground poo for on ♦ deforestation limits nesting ground

VII. Classification of Modern Birds Subclass Neornithes Superorder Neognathae order Sphenischiform order Gruiformes es order Charadriformes order Gaviiformes order Podicipediformes order Columbiformes