Birds

Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Aves Taxonomy Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Aves

The study of birds is called Ornithology. Key Term The study of birds is called Ornithology.

Origin of Birds Most scientists agree that birds evolved from a group of early reptiles. Bird fossil records are incomplete due to lightweight/delicate skeleton. Archaeopteryx is the earliest and most primitive bird ever found – fossil had teeth, long tail, hind wings, and feathers. Archaeopteryx is considered a transitional fossil between dinosaurs and birds.

Modern Birds ~ 9000 species Divided among 27 different orders Compared to 3 orders of amphibians and 4 orders of reptiles.

Similarities to Reptiles 1. clawed toes 2. scales on their feet 3. internal fertilization 4. shelled amniotic eggs

Differences from Reptiles 4-chambered heart endothermic – maintains constant body temperature respiration – air sac – 75% of air goes into air sac and 25% goes in to lungs no teeth have feathers have a beak or bill, which is a keratinized extension of their bony jaw feet adapted for swimming, grasping, and perching

Feathers A feather is a lightweight, modified scale that provides 1) insulation and 2) enables flight. Also plays role in courtship, incubation, and waterproofing Plumage – the covering of feathers on a bird. Preening – process of cleaning and rubbing oil on the feathers to keep them waterproof and in good flying condition, also gets rid of parasites. Ruffled feathers need smoothing with the bill so barbules re-connect. A preen (oil) gland is usually located above the base of the tail.

Feathers Molting – shedding of a few old feathers w/the growth of new ones flight and tail feathers are usually lost in pairs as to maintain balance do not molt at critical times such as breeding, migration or food shortage (drought) Different types of feathers

1.Down feathers 2.Contour feathers 3.Filoplume feathers 3 Types of Feathers 1.Down feathers 2.Contour feathers 3.Filoplume feathers

1.Down Feather Down feathers -Insulation & waterproofing feathers - common in young birds; fluffy w/no barbs (hooks that interlock their filaments) found underneath the contour feathers.

2. Contour Feathers Contour feathers – most common; gives body shape; used for flight; sleek, streamlined Specialized contour feathers found on wings and tail; contains barbules that stay together and move air.

3. Filoplume Feathers Filoplume feathers – long, thin shafts w/weak barbs and barbules, found around beaks. They are believed to have a sensory function, helping birds keep their feathers in order.

Parts of a Feather Shaft – continuation of quill, bears numerous barbs Barbs – branch off into barbules which overlap w/adjacent barbs/barbules with the ends interlocking, keeping feathers firm and smooth Quill – hollow; emerges from skin follicle

Color Some color is a result of pigments, other colors called structural colors, result from irregularities on the surface of the feather that diffracts white light. Color patterns are involved in species and sex recognition and sexual attraction, as well as provide camouflage.

Color Pigment Colors Structural colors Melanin produces black, brown, and tan Carotenoids produce red, orange and yellow Structural colors blue and green feathers – barb reflects blue wavelengths of light, other wavelengths pass through the barb and are absorbed. white is the complete light reflection iridescence results from interference of light waves caused by the flattening and twisting of barbules.

Adaptations for Flight… 1. have feathers 2. front appendages modified as wings wing shapes vary- some adapted for soaring and others for short quick flights 3. endothermic- helps to 1) maintain high energy levels necessary for flight 2) inhabit a variety of habitats (tropics to Antarctic) 4. high metabolic rate – eats large amounts of food to maintain energy levels 5. vertebral column modified for flight – long, flexible neck allows for bill and neck to function as a third appendage

Adaptations for Flight 6. air spaces in the bones – sturdy, thin, hollow bones; strengthened by bony crosspieces with air spaces; 7. sternum w/keel – sternum (breastbone)-where flight muscles are attached 8. four-chambered heart – rapidly moves oxygenated blood, bringing needed oxygen to cells quickly 9. efficient respiration - 2 cycles-when bird exhales, oxygenated air passes from sacs into lungs – birds receive oxygenated air when they breathe in and out; heat also carried away w/water vapor in the air that is exhaled. 10. digestive system that is adapted to deal w/large amounts of food

How Birds Fly 1. Lift of the wings must overcome bird’s weight. 2. Forces that propel bird forward must overcome drag that bird moving in air creates. Wings provide propulsion. Tail provides balance, steering, and breaking.

Types of Flight 1. flapping flight 2. gliding flight – common in seabirds (albatross) 3. circling 4. hovering – common in birds of prey (falcons) 5. soaring – use rising air currents over heated land or beside cliffs; eagle 6.diving – may be for hunting, mating, warnings

2 Groups of Birds Based on Ability to Fly 1. Paleognathae – large flightless ostrich-like birds, Kiwis – have a flat sternum with poorly developed pectoral muscles; descended from flying birds – evolved to be large because their weight did not matter. 2. Neognathae – flying birds that have a keeled sternum on which powerful flight muscles attach. (Birds can also be grouped by feeding habits)

Feeding Birds have no teeth – swallow small stones that help grind food in the gizzard. Lack bony jaw – reduces weight. Have a beak/bill that is adapted to their food source. Crop is the storage structure for food, allows for consumption of large quantities of food.

Bills

Acute sense of hearing and vision. Senses Acute sense of hearing and vision. Birds have large eyes relative to body size.

Reproduction Life cycle – (reproduction usually takes place in spring) Times vary with species and size of birds Example: Warbler Nest construction - 4 to 5 days Egg laying – 5 to 7 days Incubation – average 11 days (albatross 80 days) Fledgling – 9 to 12 days (hatchling to departure of young) Lifespan can be 5 years for some warblers, up to 30 years for some species (herring gull). Typically, the larger the bird, the longer their lifespan. Attract mates with colors, songs or calls.

Chick care… Altricial - Young are entirely dependant on parents at birth. Precocial - Young can care for themselves at birth. Eyes open with downy feather covering.

2 Types of Mating 1. monogamy – 1 partner per breeding season; 90% of all birds exhibit this behavior; female needs male to set up and defend territory, find food, provide prenatal care; some swan/geese species have 1 mate for life. 2. polygamy – 2 or more partners per breeding season

Migration Migration – innate behavior; follow the food; fly south around September, triggered by length of daylight hours; return early spring. Migration allows birds to avoid extreme climate changes and to secure food and shelter. Arctic terns fly up to about 40,000 miles/yr.

Causes of Extinction 1. habitat destruction 2. collecting bird parts, such as feathers, beaks, talons, pet trade 3. lead poisoning 4. toxic effects of pesticides, oil spills, and chemical dumping 5. competition by introduced species (cats, rats, mongoose, rabbits and goats)