Ornithology Exam 1

Characteristics of birds

- bipedal

- feathers

- beak/bill

- gizzard

- pygostyle/uncinate processes

- endothermic (40-44 degrees C)

- lay eggs

part of the stomach in which birds use to grind food in the absence of teeth, often contains rocks and grit

Gizzard

Skeletal features of birds

- uncinate processes

- furcula

- carpometacarpus

- tibiotarsus & tarsometatarus

uncinate processes

lateral projections on ribs that keep them from caving in during flight

What do birds have in common with reptiles?

- 1 occipital condyle

- 1 ear bone

- several jaw bones

- scales

- nucleated blood cells

Which is the heterogametic sex in birds?

The females with WZ chromosomes.

Taxonomy order

species, genus, family, order, class, phylum, kingdom, domain

evolution

The change in allele frequencies in a population (not individuals) over time (also defined as descent with modification from a common ancestor)

natural selection

A process in which individuals who have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

adaptive radiation

An evolutionary pattern in which many species evolve from a single ancestral species

convergent evolution

The evolution of similar adaptations after species have diverged from each other; often occurs when species occupy similar habitats

Biogeography

Nearctic - North America

Neotropical - South & Central America

Paleoartic - Eurasia + North Africa

Indomalayan - South/Southeast Asia + islands

Australasian - Oceania + islands

Avifaumas

regional assemblies of bird species

Theropoda

Direct Bird Ancestors (dinosaurs)

What features make birds therapods?

- furcula

- pneumatic bones

- air sacs

- brooding eggs

- digit loss

- feathers

Furcula

wishbone, the fused clavicles of birds

Pneumatic Bones

contain air spaces

What differs birds from ancient theropods?

- tail

- pelvis

- fingers

- tarsus

- ribs

- sternum

- teeth

Pygostyle

in birds, the fused terminal vertebrae of the spine; supports the tail feathers

Confuciusornis

first short-tailed bird

- pygostyle

- beak without teeth

Enantiornithines

- extinct sister to true birds with teeth and no uncinate processes

Ornithothoraces

true birds

Characteristics of Ornithothoraces

- feathers

- pygostyle

- fused hand bones

- uncinate processes

- pneumatic bones

- keeled sternum

- furcula

Neornithes (Aves)

encompasses all living birds

- characteristics of ornithothoraces with the addition of toothlessness

Feathers

- ancestral trait of birds that evolved in early theropods (likely originally evolved for temperature control or sexual selection)

- made up of beta keratin

What four times has flight evolved?

- insects

- dinosaurs

- theropods

- mammals

Arboreal theory

birds evolved powered flight via optimization of gliding strategies

cons: aerodynamically works, but does not explain wing strokes

Cursorial theory

flight evolved in a small dinosaur where elongated wings enhanced its ability to jump and catch prey

Wing-Assisted Incline Running

mechanism for the evolution of wingstroke is the flapping of wings to assist in climbing steep inclines

7 Parts of a Feather

- vane

- calamus (quill)

- rachis (shaft)

- barbs

- remus

- barbules

- barbicels

Vane

the flat, usually curved, surface on either side of the central shaft (rachis)

calamus (quill)

hollow central stalk of feather below skin level

rachis (shaft)

The central, stiff shaft of the feather.

barbs

Branches that extend from the rachis, forming the vane.

Ramus

the individual branch or barb that extends from the central shaft (rachis) of the feather

Barbules (distal & proximal)

Smaller branches extending from the barbs, interlocking with barbules from adjacent barbs.

Barbicels

tiny hooks that interlock to hold the barbules together

Why are feathers important?

- shape

- insulation

- waterproofing

- camouflage

- sexual selection

- flight

What are the 5 main types of feathers?

- Contour feathers

- down

- flight

- bristles

- filoplume

Contour feathers

vaned feathers that cover the entire body of a bird as well as aiding in insulation, shape, and sexual selection

- often have a plumulaceous base, sometimes with an afterfeather

Afterfeather

a second, smaller feather that grows from the shaft of a larger contour feather

What are the two types of flight feathers?

Remiges and Retrices

Remiges

wing feathers responsiblle for generating lift; consists of primaries and secondaries

Rectrices

tail feathers attached to the pygostyle, effectively used for flight control (steering and braking)

down feathers

a soft feather that covers the body of young birds and provides insulation to adult birds

bristles

- serve a sensory and protective function

- simplified, consist only of rachis with basal barbs

- usually found on the heads of birds

Filoplumes

fine, hair-like feathers with a few short barbs or barbules at the tip. They are sensory structure that aid in operation of other feathers.

Feather growth

feathers grow in feather tracts called pterylae, surrounding by apterylae

Evolution of feathers

Stage 1 - unbranched hollow cylinder, stage 2 - Plumulaceous (downy) feather, stage 3 - open pennaceous feather (formation of rachis), stage 4 - closed pennaceous feather and stage 5 - asymmetrical flight feather

Preening

process in which a bird rubs oil from an oil gland over its feathers to condition them

- maintains flight feather vanes and fights parasites

allopreening

Mutual preening during which two birds preen each other, usually around the head and neck. In many species allopreening not only keeps the plumage clean and orderly, but also helps to establish social bonds between individuals.

Uropygial gland

gland located at the base of the tail that secretes oil for preening feathers

how often do birds molt?

bird feathers are replaced at least once a year, two if they have alternative plumage

Molt Timing

- resident at any time

- Migratory birds molt prior to migration

- Long-distance migratory species can delay molting

Molt cycle

natal plumage --> prejuvenile molt --> juvenile plumage --> prebasic molt --> basic plumage --> yearly molt

In what order do flight feathers molt?

middle to outer to maintain flight ability

Two forms of feather coloration

- pigments

- structural

Types of pigments (+ one new)

- melanin

- carotenoids

- psittacofulvins

- prophyrins

- pterins (penguins)

Melanin

almost all birds have melanin:

Eumelanin - black + gray

Pheomelanin - red brown, rutous, & buff tan

Carotenoids

- reds and yellows

- yellow carotenoids are acquired through diet and then physiologically altered

Psittacofulvins

Parrot red/orange/yellow. structural colors

Porphyrins

- related to hemoglobin & chlorophyll, flourescent under UV light

structural colors

colors produced by scattering or interference, responsible for blues, most greens, and iridescence

constructive interference

The interference that occurs when two waves combine to make a wave with a larger amplitude (where the color blue comes from in nature)

iridescence

melanin granules in feather barbs arranged in regular layers results in a multi-colored appearance

4 components of flight

- taking off

- maneuvering

- stabilizing

- landing

4 major forces that act on flight

- gravity (weight)

- lift

- drag

- thrust

Two main forces of lift

- Bernoulli effect (faster = less pressure)

- angle of attack

2 types of drag

- induced

- profile

induced drag

Generated by the airflow circulation around the wing as it creates lift.

profile drag

resistance to movement that occurs as a result of the shape of an object

Alula

retractable group of feathers supported by a bird's "thumb" bone that maintains lift at lower speeds

2 modes of flight

- soaring/gliding

- flapping

2 types of soaring

- thermal

- dynamic

thermal soaring

a type of soaring in which birds use rising air thermals—rising columns of warm air—to gain height. (energy free movement)

dynamic soaring

the method in which seabirds use wind currents to travel long distances without flapping their wings, in order to conserve energy

Flapping flight

thrust & lift on downstroke, lift on upstroke

hummingbird flight

lift is generated on both the upstroke and downstroke (hovering)

bounding/intermittent flight

some birds alternate flapping and gliding/bounding flight (gliding = wings open, bounding = wings closed)

What flapping flight is energetically efficient at slower speeds?

flap-gliding

What flapping flight is energetically efficient at higher speeds?

flap-bounding

What adaptations do birds have for flight?

- asymmetrical flight feathers

- fused pneumatic bones

- uncinate processes

- keel

- pectoralis & supracoracoideus muscles

- air sacs

How are wings categorized?

- wing loading

- wing aspect ratio

Wing loading

ratio of body mass to wing area

Wing aspect ratio

length and width

What are broad wings with slotted primaries adapted for?

- slower air speeds

- reduced induced drag at wing tips (redistributed turbulence)

What are sleek, pointed wings adapted for?

- high air speeds

- reduced profile drag

Arboreal origin of flight

early bird like creatures climbed trees and glided, eventually leading to flying

Cursorial origin of flight

reptiles on ground fleeing predators ran quickly across ground got lift and got into the air (running start)

evolution of flightlessness

flight is expensive; usually island birds, diving-specialized birds, & birds without predators