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Birds Chapter 42 Origin and Evolution of Birds Section 42.1 Important characteristics Feathers – only birds have them! Wings – modified forelimbs Lightweight, rigid skeleton – hollow bones Endothermic metabolism – 104-106o F Unique respiratory system – most efficient Beak – no teeth Oviparity – eggs incubated by parents Evolution Similarities to dinosaurs: – Flexible, S-shaped neck – Unique ankle joint – Hollow bones Birds evolved from small, fast-running carnivorous dinosaurs Oldest bird fossil - Archaeopteryx Archaeopteryx Jurassic period – 150 million years ago Similar to modern birds because: – Hollow bones – Furcula: fused collarbone (aka wishbone) – Feathers Similar to dinosaurs because: – Teeth – Claws on forelimb – Long, boney tail Origin of flight Two major hypotheses: 1. Ancestors were tree dwellers that ran along branches and jumped from tree to tree, gliding wings first evolved then the ability to flap came later. 2. Ancestors were land dwellers that leapt after their prey, wings served to trap or knock down prey and over time became large enough to fly. Feathers Modified scales Two main functions: – Provide lift for flight – Conserve body heat Types of feathers: – Down feathers – insulation – Contour feathers – streamline shape, coloration, insulation – Flight feathers – on wings and tail for flight Parts of a feather Structure of the feather Follicles: tiny pits that feather develops from Rachis (Shaft): emerges from the follicle Vanes: 2 vanes on opposite side of shaft Barbs: branches of the vane Barbules: projections on the barbs with microscopic hooks Keratin: protein that makes up the feather Care of feathers Preening: use beak to rub feathers with oil secreted by the preen gland at the base of the tail. Molting or shedding of feathers periodically Characteristics of Birds Section 42.2 Skeleton & Muscles Thin, hollow bones fused together Sternum: breastbone is attachment point for flight muscles Pygostyle: last fused vertebrae that supports the tail feathers Flight muscles account for 50% of bird’s weight Metabolism Endothermic therefore require large quantities of food to generate heat Aquatic birds have a layer of fat to insulate Cannot go through long periods of time without food Digestive & Excretory Systems Path of food: mouth esophagus crop 2-part stomach (proventriculus & gizzard) small intenstine with bile from liver large intestine cloaca vent Path of wastes: blood kidneys ureters cloaca (mixes with feces) vent Digestive System Respiratory System Highly efficient Path of air: nostrils trachea branched bronchi lungs (25%) or air sacs (75%) Air sacs: – 9 total – Stores excess air – Allows for oxygenated air in lungs during exhale and inhale Respiratory System Circulatory System Rapid heartbeat – Up to 1000 beats per minute! 4 chambered heart – Like mammals Nervous System & Sense Organs Large brains (relative to body size) Some birds have color vision and/or binocular vision Some birds have a developed sense of smell Sense of hearing also important Reproduction Sperm movement: testies vasa deferentia cloaca female’s cloaca Egg movement: ovary oviduct fertilized by sperm addition of shell cloaca vent Nest Building & Parental Care Lay eggs in nest Methods of rearing young: – Precocial: active as soon as hatch – Atricial: helpless when born One or both parents incubate eggs by sitting on them and covering them with their brood patch – Thickened, featherless patch of skin on abdomen What type is this? Migration Seasonal movement of birds from one habitat to another Cues to help navigate: – – – – Position of sun and stars Topographical landmarks Magnetic field Air pressure Ornithologist: biologist that study birds Classification of Birds Section 42.3 Diversity Beak and claws infer diet and habitat Most widespread terrestrial animal on planet 23 orders of birds Order Anseriformes Examples: swans, geese, and ducks Aquatic Webbed feet Flattened bill Precocial young, care by female Order Strigiformes Examples: owls & nocturnal raptors Sharp, curved beak Sharp talons Keen sense of hearing to detect prey Order Apodiformes Examples: hummingbirds & swifts Small, fast-flying Tiny feet Long, narrow beak Order Psittaciformes Examples: parrots, parakeets, macaws, cockatoos, & cockatiels Live in the tropics Strong, hooked beak for opening seeds Two toes forward, two toes backward for climbing & perching Highly vocal Order Picformes Examples: woodpeckers & toucans Nest in tree cavities Diversity of bills based upon diet Same feet as parrots Order Passeriformes Examples: familiar birds (robins, blue jays, cardinals, etc) perching birds: 3 toes forward, 1 toe backward songbirds: males produce songs to attract mate and warn away other males – Syrinx produces sound at base of trachea Order Columbiformes Examples: pigeons & doves Plump-breasted, small heads Short neck, legs, and beak Crop secretes nutritious milk-like fluid to feed young – Crop milk Order Ciconiiformes Examples: herons, storks, raptors, & penguins World-wide distribution – Habitat determines adaptations Many are wading birds Order Galliformes Examples: turkeys, pheasants, chickens, grouse, & quail Fowl Terrestrial birds Plump-bodies with limited flying ability Order Struthioniformes Examples: ostriches & emus World’s largest birds Reduction in toe number to allow for fast running