Ornithology Exam 3

Feathers

Lightweight structures aiding in flight and insulation.

Reduced body weight

Lowers energy expenditure during flight.

Strong, light skeleton

Minimizes weight while maintaining structural integrity.

Rigid skeleton

Provides stability during flight maneuvers.

Strong pectoral girdle

Supports powerful wing muscles for flight.

Enlarged, keeled sternum

Increases muscle attachment area for flight muscles.

Large, powerful flight muscles

Generate force necessary for wing movement.

Modified wing joints

Allow folding and locking for efficient flight.

Pectoralis muscle

Contracts during downstroke to power flight.

Supracoracoideus muscle

Contracts during upstroke to assist wing movement.

Furcula

Elastic bone that aids wing motion during flight. (compresses and moves downward on the upstroke)

Lift

Upward force generated by wing airfoil shape. Increased static pressure below wing

airfoil

A part or surface, such as a wings shape and orientation control stability, direction, lift, thrust, or propulsion.

Thrust

Forward force produced by wing downstroke.

downstrokes

can be forward or downward

Primary feathers

twisted during downstroke

Drag

Air resistance opposing bird's forward motion.

Angle of attack

Wing position affecting lift and turbulence.

Turbulence

swirling air at end of wing

Flight patterns

for steady flight, thrust equals drag

thrust exceeds drag

bird ascends and speed increases

thrust less than drag

bird descends and speed slows

angle of attack (wing position)

influences turbulence

Alula

Feathered thumb reducing turbulence at steep angles.

Tail in flight

Used for steering and increasing lift during landing. often used to increase drag

Stalling

Loss of lift causing a bird to fall.

Landing

- requires slower flight (difficult)

- Tail used to generate extra lift at the end

To slow momentum birds...

- Land into wind

- Increase angle of attack

-beat wings horizontally

- swoop upward

- spread webbed feet

Wing loading

Ratio of body mass to wing area.

- limits size of flying animals

heaviest bird

Miocene condor 150 pounds

higher wing loading

can make taking off difficult

Hovering

Flight where bird remains suspended in air.

Hovering specialists

Energetically expensive: used lift through wing motion only, no thrust

Static soaring

Gliding using thermal currents without flapping. (slotted high lift wings/ high-aspect-ratio wings)

- use cliff topography to soar at times

How is static soaring movement created?

solar radiation causing air flow

Dynamic soaring

Gaining altitude by exploiting wind gradients.

- requires very thin, long wings (albatrosses)

best angle of wing for the least amount of turbulence

slightly above horizontal

most common wing shape

Elliptical

Powered flight pattern

undulating (smooth up and down pattern)

Migration

Regular, seasonal, 2-way movements between 2 areas

- don't usually move North

Migration patterns

Predictability and seasonal variability in food determine the migration strategy

Migration Trade-offs

Advantages: avoid harsh winters, seasonally abundant foods to feed offspring

Disadvantages: loss of energy and reduced survival associated with migration

are facets of migration genetic or heritable? (yes or no)

yes

Different Routes of migration

- follow landmarks

- cross oceans

- straight lines

- circular routes

North American land bird migration

N-S

Europe & Asia bird migration

E-W

Shore bird migration pathways

- Spring and Fall pathways differ ALOT

- Several important stop areas (rest & eat for energy)

- global warming may affect this

Migration altitude

- relatively low (<4,000m)

- passerines are lowest (<2,000m)

- Shore birds highest

Diurnal migration altitude

lower (to see land marks)

Migration over water altitude

Higher (no land marks)

Highest migration altitude recorded

Bar-headed geese (8,500=27,800 ft)

Daily Migration Timing

Daytime Migration:

- Soaring birds rely on thermals

- Swifts and swallows feed during migration

- Misc. others (corvids, cormorants)

Night Migration:

- Most passerines

- celestial navigation cues

- saves energy

- less predation risk

Seasonal Migration Timing

- Precise

- Photoperiod (most important for migration/pre-migration)

- departure dates can vary dependent upon weather

- Climate change (mismatch hypothesis)

mismatch hypothesis

Birds breeding at the wrong time due to climate change

Tailwind

Winds that blow in the direction of the flight (Birds prefer using these winds)

headwind

a wind blowing in a direction opposite of flight (birds will stay on the ground)

waterfowl grand passages

Headwinds stop after a few days, then tailwinds come and a massive amount of birds fly away at once

Songbird fall-outs

all song birds flying in the sky come down at once

Hyperphagia

excessive eating (preparation for migration)

Navigational Cues

- orientation of the sun

- Geomagnetism

Magnetic compass of bird (geomagnetism)

- Photopigments in retina (innate)

- Magnetite particles in head (can be trained)

seasonal monogamy

pair bond is formed for a breeding season

lifelong monogamy

one mate for the whole life

- permanent territories (eagles)

- Social status (geese)

Polygyny

One male, several females.

Polyandry

One female, several males.

Polygynandry (Ostriches)

multiple males, multiple females

Communal nests (polygynandry)

Multiple bonded pairs share a nest

percent of birds that are monogamous

90%

Types of Polygyny

- resource defense

- female defense

- lekking

- scramble competition

serial polyandry

female lays a clutch with each of a series of males throughout the breeding season

resource defense polygyny

males defend territories rich in resources that are used by and attract females

female defense polygyny

Polygynous males directly defend several females.

Lek polygyny

polygynous males attract several mates to a display territory

• Prairie nesting grouse

• Bowerbirds

• Birds-of-paradise

- mates raise young alone

Resource defence polyandry

Females defend territories to attract multiple males

Plural Breeders

Several males and females share a nest and raise a communal brood

• Groove-billed anis - extreme predation risk

• Acorn woodpecker - protect their food cache

Promiscuity in birds

- some consider lekking to be this

- hummingbirds mating with any female that approaches

- most ornithologists don't believe in promiscuity

Extra pair copulations

• 70% displayed some infidelity

• But only 34% had >10% of offspring fathered by males other than the mate

brood parasitism

one egg-laying species benefits by having another raise its offspring

Intraspecific Brood Parasitism (IBP)

Nest dumping

- laying eggs in nests of the same species

- common

- happens with limited nesting spots

Interspecific Brood Parasitism

Facultative

- Lay some eggs in their own nest but before then they lay their eggs in other birds species nests

• Redheads parasitize canvasbacks before laying in their own nests

• Eggs are not limited

• "Double dipping

Obligate

- Only lay eggs in other species nests do NOT make their own nests or raise young

• European Cuckoo

• Brown-headed cowbird

Obligate brood Parasitism

- Often sneaky when laying eggs

- Many mimic eggs of the hosts

- Some parasitic young kill offspring of hosts

- Young are not heavily imprinted on hosts

cooperative breeding

- caring for young of other individuals (i.e., helpers) (8%)

◼ Much more common in old world birds (e.g., bee-eaters, hornbills, old world warblers)

◼ Few North American birds (e.g., Florida scrub jay, Red-cockaded woodpecker)

Explanations of cooperative breeding

• Kin selection - caring for relatives

• Limited nest sites (acquire later from parents)

• Gaining parental experience

• Increase survival by staying with parents

Does cooperative breeding increase offspring survival?

Yes; well documented

Does cooperative breeding increase long-term fitness of helpers?

Yes; well documented

Display strategies

- Passerines establish nesting territories and display them

- Waterfowl display to acquire mates during winter before migration

- Lekking species display communally

classic example of sexual selection

birds of paradise

Nest functions

- thwarting predators

- protecting eggs and young from the elements

Nest types

- Cup shaped (phoebe)

- Domed nests (cliff swallow)

- Platforms (pigeon)

- Cavity nest

- Scrapes in pebbles/sand (killdeer)

- Mound nest (megapodes)

- without nest (white turn, penguins)

Nest sites

- generalist (carolina wren)

- specialist

bird eggs

amniotic

amnion

Membrane that encloses the embryo in protective amniotic fluid

ova

unfertilized eggs

bird ovaries

Female only has one functional ovary on the left side

Egg development

- stimulated by estrogen

- Yolk is formed and deposited before ovulation (release the egg into oviduct)

- on the second day of egg formation a second egg will form and on the third day a third egg will form ect.

- first egg formed is biggest egg

- 6 days of development before ovulation

infundibulum

the funnel-shaped opening into the fallopian tube near the ovary

albumen

egg white

egg shell formation

takes 20 hours then the next 4 hours its laid

Laying rates

Most birds lay an egg per day

geese laying rate

1.5 day egg laying rate