Birds Flashcards
Uniformity in structure
Birds
Flight restricts morphological diversity
Forelimbs
Modified into wings
Hind limbs
Adapted for walking, swimming, or perching
Taxonomy
What are the 2 groups of living birds
- Paleognathae: Large flightless birds
- Neognathae: All other birds
Theories for the evolution of flight
Arborial Theory (more likely)
Ancestors climbed to high places (e.g. trees) and glided down
Theories for the evolution of flight
Cursorial Theory (less likely)
Ancestored flapped their wings to launch into air from ground
Adaptations for flight
- Feathers
- Skeleton
- Muscular system
- Respiratory system
Adaptations for flight
Feathers: Roles
- Mating
- Territorial dominance
- Regulation of body T°
- Camoflauge
- Flight
Adaptations for flight
Feathers: Structure
- Shaft: calamus + rachis
- Vanes: Soft surfaces of the feather
- Outer vane = leading edge (smaller & thinner)
- Barbs: Emerge from rachis
- Barbules: Emerge from each barb
Adaptations for flight
Feathers: Types
- Contour: Outermost feathers that give the bird its form
- Down: Beneath contour feathers, without prominent rachis
- Filoplumes: Hairlike feathers
- Powder downs: Tips disintegrate as they grow, releasing a talc-like powder which helps waterproof the feathers
Feathers: Types
Types of Contour feathers
- Remiges: Flight feathers, often the largest, attached by ligamets are directly to bone
- Rectrices: Tail feathers, attached to each other by ligaments, only innermost attached to tailbone
- Coverts: Small feathers that overlay and border remiges and rectrices, help shape the wings and provide insulation
Adaptations for flight
Feathers: Molting
- Periodically shed and replaced (during periods w/ lower energy demands)
- Remiges/rectrices molted in pairs
- Plummage can change with molt
Skeleton
Adaptations for flight
- Light & delicate skeleton
- Bones holow (laced with air cavities)
- Bones reduced in number & fused together
- Lighter skull/neck + heavier legs = lower center of gravity
- Keel: Point of attachemnt for flight muscles
Adaptations for flight
Muscular system
- Locomotor muscles: massive compared to other muscles
- Pectoralis: Depresses the wings in flight
- Supracoracoideus: Raises wings
- No muscles in feet – resistant to freezing
- Tendons extend from leg muscles to toes – tighten automatically when perched
Adaptations for flight
How is the respiratory system of birds adapted to flight?
- Air sacs throughout thorax/abdomen/bones connected to lungs
- Parabronchi
- Continuous flow of O2 through lungs
