Vertebrate Zoology 8 - Birds

What are Archosaurs?

A group of diapsid reptiles with two additional skull openings, including crocodilians, pterosaurs, and dinosaurs (including birds).

What are the three types of vertebrate wing structures?

• Pterosaurs: Membrane from elongated 4th finger to hindlimb.

• Birds: Feathered forelimbs.

• Bats: Membrane stretched between elongated fingers.

What key feature defines avian-lineage archosaurs?

They have "mesotarsal" ankle joints, which allow a single hinge movement.

What is the function of metatarsals in birds and dinosaurs?

They provide a digitigrade posture, essential for efficient bipedal locomotion.

How is the femur oriented in birds compared to crocodiles?

• Birds have an offset femoral head for an upright stance, while crocodilians have a more ventral acetabulum allowing a sprawling posture.

What feeding adaptation did Pterodaustro have?

Over 1,000 bristle-like teeth for filter feeding.

How do modern birds differ from non-avian dinosaurs in tail length?

Birds have a reduced tail, whereas dinosaurs had long tails for balance and locomotion.

What happened to pterosaurs and non-avian dinosaurs at the end of the Cretaceous?

Both went extinct, but birds survived and diversified.

Name three reptilian traits found in Archaeopteryx

• Antorbital fenestra.

• Reptilian teeth.

• Unfused bones.

What modern bird behavior is Archaeopteryx’s brain size comparable to?

Social complexity similar to farmyard chickens.

What skeletal adaptations evolved after Archaeopteryx?

• Expanded braincase

• Fused manual bones

• Fused pelvic bones

• Pygostyle (fused & reduced tail vertebrae)

• Uncinate processes on ribs

• Expanded sternum with keel

What is the scientific class that includes all living birds?

Class Aves

What are the two major groups of living birds based on palate structure?

Paleognaths and Neognaths (all other birds)

Name two examples of ratites (Paleognaths).

Ostrich, emu

What is a defining skeletal feature of ratites (paleognaths)?

They lack a keel (carina) on the sternum, making them flightless.

What is unique about paleognath parental care?

Males incubate the eggs and care for the chicks

What is the major distinguishing feature of neognaths?

Their palatines are juxtaposed rather than large and separate.

What is the basal group of neognaths?

Galloanserae (fowl: ducks and chickens)

What are the two main orders in Galloanserae?

Anseriformes (ducks, geese, swans) and Galliformes (chickens, pheasants, quail)

What is a unique feature of the Magpie Goose?

Its feet are only partially webbed.

What percentage of living bird species belong to Neoaves?

About 95%

What order do perching birds belong to?

Passeriformes

What adaptation helps passerines perch effectively?

Anisodactyl feet (three toes forward, one toe backward)

What is the function of the syrinx in passerines?

It is a vocal organ that allows songbirds to produce complex sounds.

How do falcons differ from hawks?

Falcons kill prey with their beaks, while hawks use talons.

What evolutionary change in birds led to diverse feeding adaptations?

The loss of teeth and the development of the beak.

What is the function of the sclerotic ring in birds?

It supports the eyeball in the orbit.

Which bone in the bird skull allows for kinetic jaw movement

The quadrate bone.

What structure supports the bird tongue?

The hyoid apparatus.

How is the woodpecker’s hyoid apparatus specialized?

It extends around the skull and contracts to project the tongue forward.

How does the gizzard aid in digestion?

It is a muscular organ that grinds food, sometimes with the help of gastroliths (swallowed stones).

What kind of diet requires a larger crop and gizzard?

A seed-based diet.

What is a unique feature of ostriches regarding digestion?

They swallow pebbles to help grind food in the gizzard.

What is the main function of the large intestine in birds?

Water and electrolyte absorption.

How do birds excrete waste?

Through the cloaca, which combines urinary, digestive, and reproductive functions.

Do birds have a bladder?

No, they excrete uric acid directly through the cloaca.

How does bird respiration differ from mammals?

Birds have a unidirectional airflow system for constant oxygen exchange.

What is the function of avian air sacs?

They help maintain airflow and lighten the skeleton.

What is the role of the aspiration pump in birds?

It moves air through the lungs using rib cage expansion and contraction.

What are the different types of remiges (flight feathers)?

Primary, secondary, and tertiary remiges.

What is the function of the alula in birds?

It helps control airflow during slow flight, landing, and hovering.

How do most birds copulate?

By cloacal apposition (contact between cloacas).

What are the key structures in the male reproductive system?

• Testes (larger during breeding),

• Vas deferens (transports sperm)

• cloaca (common exit for sperm, urine, and feces).

How many functional ovaries do most birds have?

Only the left ovary; the right one regresses after initial development.

Where does fertilization occur in birds?

In the infundibulum, within 15 minutes of ovulation.

What is the function of sperm storage tubules (SST)?

They store sperm at the junction of the uterus and vagina, allowing delayed fertilization.

What are the major steps of egg formation in birds?

• Ova enters infundibulum (fertilization)

• Albumen (egg white) added

• Shell membranes deposited

• Mineralized shell forms in the shell gland (uterus)

• Laid via cloaca (oviposition)

What determines the shape of a bird’s egg?

Different evolutionary adaptations: conical eggs roll in a tight circle (e.g., cliff-nesting birds), spherical eggs are stronger, and elongate eggs may be ancestral.

What is the purpose of a brood patch?

A featherless, highly vascularized area on incubating birds to transfer heat to eggs.

How do birds regulate incubation temperature?

By turning eggs to distribute heat evenly and prevent membranes from sticking.

What is an ‘egg tooth’?

A temporary, keratinized structure on a chick’s beak used to break the eggshell.

What are the two main types of hatchling development?

• Altricial chicks: Blind, naked, helpless (e.g., songbirds).

• Precocial chicks: Eyes open, mobile, self-feeding (e.g., ducks, waders).