Ornithology test 4

Circadian Rhythm

daily activity cycles 24 hours

circannual rhythm

activity cycles 12 months long

Entrainment

Using environmental cues to fine tune circadian rhythms

entrainment causes circadian rhythm to become

free-running

free running circadian rhythms

activity patterns that drift from the 24 hr cycle

innate internal clock

mechanism for keeping approximately 24 hr cycle without external cues

Zeitgeber

Environmental event that entrains biological rhythms; a "time giver"

circannual cycles also rely on

innate internal clock and zeitgeber

photoperiod

most common zeitgeber for circannual cycle

photosensitive period

period when exposure to light stimulates physiological changes in birds

most common zeitgeber for north american birds

photo-period (doesnt work at equator)

Some tropical birds ...

do not follow twelve month cycles (sooty terns breed every 9.6 months)

response to zeitgeber shaped by

evolution

Global warming is causing and evolutionary response in a few species

earlier spring migration and earlier first egg date

Calls

Brief sounds with relatively simple acoustical structure

-year round

-Both sexes

songs

more complex sounds than calls generally composed of 5 or more notes seperated by pauses

-breeding season only

-males only

syrinx

avian voice box

syrinx is functional equivalent to

human larynx

sound produced by

1. vibrations of membrane

2. forcing air through passageway

dual sound source theory

bird have independent control of right and left sides of syrinx (tested with wood thrush)

-cut nerves going to one side of syrinx and only one part song lost

Sonograph

plot of frequency across time

most oscine passerines

learn the songs they sing

Song learning in birds

1. must hear conspecific during learning period

2. must hear self-sing during subsong period

during critical song learning period tutor songs are filtered through a

template in the brain

Song dialects

regional variations of species-specific songs

Not all birds learn their song

brown headed cowbird

-innate song template

-no critical song learning period

- but must practice as young bird

functions of bird songs

signaling social status in male-male competition and attracting females during mate choice

what happens when devocalized male seaside sparrows

# of fights and intrusions increased

song might be an honest signal of

stamina, brain structure, and cellular respiration

dawn chorus

heightened volume of bird song at dawn

dawn song hypothesized to signal

male quality as only males in best condition can sing before foraging

Repertoire size

number of distinct songs that are sung by an individual (varies by species) (may signal brain quality)

mimicry

using the songs of other birds or other sound sources as part of song

territory

an area of exclusive resource use defended by one or a small group of individuals

Home range

an area habitually used by a bird -- NOT EXCLUSIVE

breeding territories

type a, type b, type c, type d

type A breeding territory

all purpose-- mating, nesting, and foraging site for parents and young

type B breeding territory

mating and nesting territory, but not feeding

type C breeding territory

mating only, leks

type D breeding territory

small nesting territory, not usually considered a true territory

factors that determine territoriality

1. food density

2. nest site availability

3. predation pressure

most dominance hierarchies are

linear

Determinants of Dominance

1) Size and physical attributes

2) Age and experience

3) Home court advantage

4) Motivation

size and physical attributes

all else equal the larger and stronger wins

Age and experience

older birds with prior territorial experience almost always wins

Status Signal

a morphological trait that reliably indicates resource holding potential

Delayed Plumage Maturation

not attaining definitive (adult) plumage until after the first potential breeding season

subadult plumage is a type of

status signal

black headed grosbeak subadult plummage led to

less aggression towards these sub adults

It takes how long for black-headed grosbeak to get best territories

years

status signals can also work within an

age/sex class

status signals are ______ because cheaters are punished

honest

Site residency (home court advantage)

Territory owners almost always defeat invaders

Motivation

more motivated birds defeat less motivated birds

best combination for fighter

big, experienced, home turf, really wants the girl

Testosterone

male steroid hormone

proximate control for aggressive behavior and dominance

can change territorial behavior

what testosterone do to sparrow in studies

males expanded territories and became polygynous

Tradeoff of testosterone and parenting

more singing less parental care of young

2 broad nest categories

cup nest and cavity nest

2 important groups of cavity nesters

excavators - dig their own cavity

non-excavators - use existing cavities

Nest complexity

continuous variation from very simple to very complex

some species tie complex knots to make nest

Nest construction materials

sticks, mud, saliva in different ratios depending on bird

2 general strategies for clutch size

fixed clutch size - always the same number of eggs

variable clutch size - range # eggs

What determines clutch size?

parental ability and risk of loss

Incubation

keeping eggs warm with parental body heat

what bird use heat from rotting vegetation to warm eggs

brush turkey

brood patch

bare patch on breast that becomes filled with fluid

like a pillow for transferring heat

typically- only females

Who incubates the eggs?

female only = most common

male and female = uncommon

male only = rare; phalaropes

two adaptations for hatching

hatching muscle and egg tooth

hatching muscle

strong muscle on back of neck used to break out of egg

egg tooth

small project at tip of bill on present at time of hatch

Precocial young

at hatch are mobile, covered in dense down, and feed themselves. Mainly Galliformes and Anseriformes

Artricial young

At hatch are immobile, naked or nearly naked, and cannot feed themselves

2 patterns of incubation

incubate after all eggs are laid or begin incubation with first egg

synchronous hatching

all chicks hatch at once (incubated after all eggs laid)

Asynchronous hatching

chicks hatch on different days (begin incubation on first day)

precocial young must hatch

synchronously

asynchronous hatching can lead to _____________

siblicide and brood reduction

Brood reduction

letting the youngest/weakest chicks starve if food is limited

Siblicide

killing your siblings so you don't have to compete with them and a form of brood reduction

brood parasitism

Laying eggs in other birds' nests.

2 forms of brood parasitism

facultative brood parasites and obligate brood parasites

facultative brood parasites

are capable of building nest and raising young but somtimes broos parasite

obligate brood parasites

incapable of building nest or raising young. must parasitize another species

host bird species fall into these two groups

rejector species and accepter species

rejector species

sometimes recognize cowbird eggs and reject them

accepter species

almost never recognize cowbird eggs; are very vulnerable to parasitism

Rejector species (what birds)

all are edge/grassland species. history with cowbirds.

edge of prairie =

edge of cowbirds

accepter species (what birds)

interior forest birds that has had no exposure to cowbirds until forest were cleared

Cooperative breeding

more then 2 birds of the same species provide care in rearing the young from one nest

helpers

birds other than the core breeding pair that helps raise offspring (almost always offspring of breeders)

example of cooperative breeders

red-cockaded woodpecker, scrub-jay, acorn woodpecker, Harris HAwk

nestling

young bird still in the nest

fledgling

young bird out of the nest but dependent on parent

fledging

act of leaving the nest

Bird Growth

Birds grow very rapidly and reach adult body size by fledging. Any flying bird is adult sized

resident birds

species present throughout the year

wintering birds

species present only during non-breeding season

breeding migrant

species present only during breeding season