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Birds
Characteristics• Forelimbs wings• Feathers (of beta keratin, same protein in scales of legs)
• Flight requires lots of energy– Features that reduce weight – Features that increase energy production– Adaptations for flight:
• No urinary bladder• Single ovary • Reduced gonads• Skeletal modifications• One-way respiratory system (w/ parabronchii)• 4 chambered heart (evolved independently of mammal heart)• endothermic
Benefits of flight
• Increased foraging ability• Massive migrations to seasonal food sources• Feeding on airborne insects (new food resource)
• Dispersal• Escape from predators
Keel of sternum (#4)
Furcula (wishbone/collarbone) # 5
Flightless Birds• Ratites
– lack sternal keel– pectoral muscles are reduced/small
– Ostrich (Africa)– Rhea (south America)– Kiwi (new Zealand)– Cassowary (Australia & new guinea and surrounding is.)– Emu (Australia and Tasmania)
Penguins are flightless • But have keel and powerful pectoral muscles because they use
wings to “swim” under water.
Respiratory System• No diaphragm• Air sacs act as bellows• One-way air flow through lungs• Parabronchi• No mixing of residual and fresh air• Counter current like gas exchange
Vocalize w/ Syrinx (not larynx)
membrana tympaniformis
Digestive System
• No teeth• CROP—stores food• Proventriculus—released digestive enzymes• Gizzard (ventriculus)—mixing and mechanical
digestion
EXCRETORY SYSTEM
• Kidneys produce uric acid• No urinary bladder• Ureters connect to digestive track just
upstream of cloaca• Bird “poop” is a mix of feces and uric acid
(white stuff)• They don’t hold it (much) it comes out on
demand
Nervous System
• Flight requires well developed nervous system• Vision– Complex eyes– Large orbit of skull
• Disproportionately large brain– Processing visual information– Integrating sensory and motor function for flight– Intelligent!– Complex behaviors
Reproduction
• Internal fertilization– Cloacal contact (kiss)
• Eggs/oviparous– Adaptation for flight
• Often biparental care• Most birds are monogamous (with lots of cheating)
– Because off spring require so much care—takes both parents– Incubating– Feeding young (young have high energy demand so need lots
of food)– Protecting young