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: 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. 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: Types of feathers: 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 video

Parts of a feather

Structure of the feather Follicles: tiny pits that feather develops from 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 video

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 4 chambered heart 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 Altricial: 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

Migration video 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

Bird Beaks and Feet