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 (104° F to 108° 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 Camouflage Covered in feathers (modified reptilian scales) Develop from 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
Feathers Attract Mates Male and female cardinals
Feathers Preening- Pulling feathers to relink connections Follicles- Small sacs in skin where feathers develop Two types: Contour 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) Preening- Pulling feathers to relink connections Preen gland- Secretes oil to clean and waterproof feathers At base of tail Down feathers- Insulate under contour feathers
Bird Feathers
Amazing Bird Flights Hummingbird 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 Turkey 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 Robin Mocking bird
Bird Adaptations Adaptations based on habits and diet Sea gull Beak (bill) Legs Feet Some adaptations include Stream-lined bodies for flying over water Low-light vision for feeding at night (nocturnal) Wings adapted for swimming Sea gull Barn owl
Flightless Birds Ostriches (Africa) & Emus (Domesticated) Largest birds Body to heavy for flight Penguins (Antarctica) Adapted wings for swimming Emperor penguin family
Avian Adaptations
Avian Adaptations
North American Flyways
Long Migration Flight
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