Section 1 Origin and Evolution of

BirdsChapter 42

Objectives

• Identify and describe seven major characteristics of

birds.

• List three similarities between birds and dinosaurs.

• Describe the characteristics of Archaeopteryx.

• Summarize the two main hypotheses for the

evolution of flight.

Birds (Aves)

42-1

I. Origin

•Evolved from small fast running reptiles (Dinosaurs)

•Poor fossil record because bones are fragile,

and hollow, and don’t preserve well. So

scientists disagree on which particular line of

reptiles gave rise to birds.

A. Archaeopteryx (“ancient wing”) (1861)– may

represent a link between birds and reptiles.

1. Jurassic period (150 mya)

2. Like reptiles – large skull, teeth, claws, tail

3. Like birds – Furculum – fused collarbone

“wishbone” and feathered wings.

B. Hypothesis on their evolution

1. Arose 230 mya from thecodonts.

a. Walked on hind legs

b. Some may have been tree dwellers

c. Large collarbone

2. Arose directly from a group of dinosaurs called

coelurosaurian theropods about 150 mya.

a. Later – Hesperornis (90 mya) – large,

flightless, diving bird. Resembled the

modern loon.

b. And – Ichthyornis – large wings, may have

been a strong flyer.

42-2 Characteristics

•Feathers.

•Bones are thin and hollow.

•Forelimbs function as wings; used for flight, not

grasping (most species)

•Hind limbs with claws.

•Toothless, horny beak.

•Endothermic (warm-blooded).

•Four-chambered heart with a single right aortic arch.

•Oviparity - Amniote egg encased in a shell.

•Most incubate eggs in a nest.

I. Feathers – modified scales that provide lift and

Insulation.

•Down – soft, fluffy, cover the body in nestling birds,

provide insulation in adults.

•Contour – give streamlined shape, provide

coloration and insulation.

•Flight – specialized contour feathers on the wings

and tails.

•Hairlike filoplumes or pinfeathers, and dust-filtering

bristles near the nostrils.

A. Structure

1. Follicles – pits in skin where feathers develop.

2. Shaft – emerges from follicle with two vanes on

each side.

3. Each vane has many branches called barbs.

a. Each barb has many projections called

barbules that are equipped with microscopic

hooks.

B. Preening – using their beaks to rub their feathers

with oil secreted by a preen gland located at the

base of the tail.

C. Molting – replacing its flight feathers.

1. Late summer between breeding and migration.

2. Some undergo a spring molt prior to courtship.

II. Beaks and Feet

•Hawks and eagles – powerful beaks and clawed

talons for ripping flesh.

III. Skeleton / Muscles

A. Bones are thin and hollow, many are fused to

make the frame more rigid.

1. Anchor for powerful breast muscles (flight

muscles account for 50% body weight) and leg

muscles.

B. Sternum (keel or breastbone) – attachment for

flight muscles.

C. Furculum – wish bone

D. Pygostyle – terminal fused vertebrae, supports

the tail feathers

E. Flight (watch video).

IV. Endothermy (warm blooded)

A. 400 – 420 C (104 – 107 F)

•Can inhabit both cold and hot climates

B. Rapid breathing and lots of food required.

C. Conserve heat by fluffing feathers for insulation.

V. Digestion

A. Can be quick

B. Blackberries in 45 minutes

C. Magpie can digest a mouse in 3 hours (versus 3

days in a snake)

D. Cannot chew

E. Pathway

1. Mouth

2. Esophagus

3. Crop (enlarged part of esophagus) – stores and

moistens food

4. Proventriculus – gastric fluids

5. Gizzard – muscular organ that kneads and

crushes food. (contain small stones to help

grind the food)

6. Pyloric sphincter

7. Small intestine also called the duodenum

8. Large intestine

9. Cloaca

VI.Excretion

A. Most do not store liquid waste (Why?)

B. Highly concentrated uric acid is sent to the cloaca

by ureters from kidneys.

C. Uric acid along with feces is excreted in a semi-

solid, usually white mass.

VII. Respiration (need lots of oxygen, Why?)

A. Syrinx or song box.

B. 75% of the air by-passes the lungs, going directly

to the air sacs.

C. Air sacs - 9 sacs that extend out from the lungs

and connect with air spaces in the bones. Helps

not only in respiration but also reduces the bird’s

density.

D. When the bird exhales CO2 from its lungs, O2 is

forced into the lungs from the air sacs by way of

small tubes. Thus birds received O2 during

inhalation and exhalation.

VIII. Circulatory

A. Four-chambered heart

B. Single aortic arch

C. Hummingbird – 600X / Min

D. Chickadee – 1000X / Min

E. Human – 70X / Min

IX. Nervous

A. Large brain for size

B. Flight Control

C. Smell

D. Hearing

E. Taste

F. Vision

1. Those with eyes facing front, binocular vision.

X. Reproduction

A. Males – sperm passes from testes - vasa

deferentia – cloaca.

B. Females - one ovary – oviduct (fertilization &

calcification of shell)

C. Unfertilized egg

1. Nucleus, cytoplasm, yolk.

D. Fertilized egg

1. Albumen – egg white

2. Chalaza – ropelike strands of support

3. Shell membrane

4. Shell gland – secretes a protective calcium

carbonate shell to surround the egg.

XI.Incubation – warm egg by sitting on them.

A. Brood patch - a thickened, featherless patch of

skin on the abdomen.

B. Egg tooth – helps break egg, falls off after

hatching.

C. Precocial young – active as soon as they are

hatched. (ducks, chickens)

D. Altricial young – nest bound. Blind, naked, and

helpless. (hawks, eagles, robins)

XII. Behavior

A. Territoriality

B. Courtship – behavior to attract a mate.Birds of Paradise Dance.

C. Nest building

D. Migration – landmarks, magnetic clues, air

pressure.

42-3 Classification

No notes. Show powerpoint from text just for

information.

Section 3 Classification

Chapter 42

Diversity, continued

Order Anseriformes

• Includes swans, geese, ducks and other

waterfowl

– Webbed feet

– Flattened bill

– Precocial young

Section 3 Classification

Chapter 42

Diversity, continued

Order Strigiformes

• Includes owls

– Nocturnal

– Keen vision with forward facing eyes

– Predators

– Keen hearing

Section 3 Classification

Chapter 42

Diversity, continued

Order Apodiformes

• Includes hummingbirds and swifts

– Small birds with tiny feet

– Fast flying, some can hover

– Insectivores and nectar feeders

Section 3 Classification

Chapter 42

Diversity, continued

Order Psittaciformes

• Includes parrots, parakeets, macaws, cockatoos, cockatiels

and their relatives

– Seed and fruit eaters

– Strong hooked beaks for opening seeds

– Two forward facing and two backward facing toes, for

climbing and perching

– Vocal birds, some can mimic human speech

Section 3 Classification

Chapter 42

Diversity, continued

Order Piciformes

• Includes tree dwelling birds such as woodpeckers, honeyguides and toucans.

– All nest in tree cavities

– Two forward and two backward facing toes

– Woodpeckers have sharp, chisel-like bills

– Toucans are fruit eaters and have large bills

Section 3 Classification

Chapter 42

Diversity, continued

Order Passeriformes

• Includes robins, warblers, blue jays, wrens, and other common North American birds

– Perching birds with three toes forward and one backward, with enlarged rear toe for grip

– Seed, fruit, insect, and nectar feeders

– Many are songbirds. Males use elaborate songs to attract females. The song is produced in a structure called the syrinx.

Section 3 Classification

Chapter 42

Diversity, continued

Order Columbiformes

• Includes pigeons and doves

– Large breasts and small heads

– Fruit or grain eaters with small beaks and

short legs

– Both sexes feed young with nutritious fluid

produced in the crop, called crop milk

Section 3 Classification

Chapter 42

Diversity, continued

Order Ciconiiformes

• Includes herons, storks, ibises, egrets, raptors,

vultures and penguins

– Highly diverse group

– Many are wading birds that eat fish and frogs,

with long legs, long neck, and long bill

– All are carnivorous

Section 3 Classification

Chapter 42

Diversity, continued

Order Galliformes

• Includes turkeys, chickens, pheasants, grouse, and quails

– Commonly called fowl

– Usually plump bodies, may be poor fliers

– Grain and insect eaters

– Precocial young

Section 3 Classification

Chapter 42

Diversity, continued

Order Struthioniformes

• Includes ostriches, emus, rheas, and cassowaries

– Includes the worlds largest birds

– Fightless birds with small wings and long powerful legs for running

– Ostriches can reach speeds of 55 mph

– Ostriches have two toes per foot