Chapter 21-Birds

Class Aves- Birds• ~8,700 species• Forelimbs modified into wings• Amniotic eggs (hard-shelled)• Scaled feet and legs• Strong, light-weight skeleton• Endothermic metabolism (104Endothermic metabolism (104°° F to 108 F to 108°° F) F)• Completely divided ventricle

– Oxygenated and deoxygenated blood completely separate• Highly efficient lungs• Syrinx- Bird’s song box

Bird Heart

Highly Efficient Lungs

• One-way air flow• Air sacs store gas (more

efficient)• Lungs exposed to only

oxygenated air• Blood travels in opposite

direction

• Endothermic metabolism, completely divided ventricle, and efficient lungs account for energy needed for flight

Highly Efficient Lungs

Bird Skeleton

• Thin• Hollow• Many bones fused for

sturdy muscle attachment• Keel- Enlarged

breastbone and fused collar bone– Breast muscles attachment

(30% of weight)

Class Aves- Birds

• Brain to body size ratio second only to mammals• Digestion:

– Beak lacks teeth– Crop- Expanded portion of esophagus stores food– 2-chamber stomach:

• Proventriculus - 1st – Digestive acids partially break down food• Gizzard- 2nd – Muscular; grinds and crushes

– Waste exits cloaca– Covert nitrogenous wastes to uric acid in a harmless white

paste form

Feathers

• Covered in feathers (modified reptilian scales)– Develop from follicles follicles (tiny pits in

skin)– Molt feathers individually– Also function as camouflage or

attracting mates• Sexual dimorphism- Males and

females have different appearances– Males more brightly colored to

attract females

CamouflageCamouflage

Feathers Attract MatesMale and female cardinalsMale and female cardinals

Feathers• Follicles- Small sacs in skin where feathers develop • Two types:

– Contour feathersContour feathers- Cover body and give shape• Flight feathers- wings and tail• Protect and streamline • Rachis- Broad, flat part of feather

– Vane- central shaft of feather– Branches (barbs) w/barbules (projections with hooks) interlock– Quill- bottom section of rachis (calamus)

• PreeningPreening- Pulling feathers to relink connections– Preen glandPreen gland- Secretes oil to clean and waterproof feathers

» At base of tail• Down feathersDown feathers- Insulate under contour feathers

Bird Feathers

Amazing Bird Flights

• Hummingbirds flap their wings rapidly (20-80 beats per second)– Smallest birds

• Migrating birds can travel up to 2,000 miles in 6 days

• Gulls and vultures use upward air movement to use little energy

HummingbirdHummingbird

Turkey VultureTurkey Vulture

Bird Reproduction and Offspring • Monogamous- many bird species have mating pairs

and mate for life• Clutch- a group of eggs in a nest

– Incubate- Male or female parents keep eggs warm– Albumin- Egg white (protein)– Altricial- birds helpless at birth

• Few eggs at a time• Stay in nest a long time• Ex: songbirds (i.e. American Robin)

– Precocial- birds well developed at birth• Large numbers of eggs• Feed themselves• Ex: Ducks and chickens

Bird Diversity• 28 orders (see page 329)

– 60% order Passiformes (song birds)

– 5,300 species; largest group of terrestrial vertebrates

RobinRobin

Mocking birdMocking bird

Bird Adaptations • Adaptations based on habits and diet– Beak (bill)– Legs – Feet

• Some adaptations include– Stream-lined bodies for flying

over water– Low-light vision for feeding at

night (nocturnalnocturnal)– Wings adapted for swimming

Sea gullSea gull

Barn owlBarn owl

Flightless Birds

• Ostriches (Africa) & Emus (Domesticated)– Largest birds– Body to heavy for flight

• Penguins (Antarctica)– Adapted wings for

swimming

Emperor penguin Emperor penguin familyfamily

Avian Adaptations

Avian Adaptations

North American Flyways

Long Migration Flight

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