Ornithology exam 2

Christian Cooper

birder

J. Drew Lanham

professor, wildlife biologist, conservationist, author of rules for the black birder

Rules for the Black Birder

• black birds matter

• follow the rules

• throw out general impression, shape, size

• diversify birding habits

• celebrate different life history strategies

• listen to songs outside normal range

• dispersal is natural, colonization is not

• altriusm is part of avian ecology

• molt is part of annual cycle

American Orno Society name change proposal

proposed to change common names of birds named after colonizers, murderers, etc.

Zugunruhe

caged migratory passerines become restless just before time at which they would migrate in the wild - bird will jump/flutter until midnight

Entrain

process by which internal biological cycle synchronizes with external cues called Zeitgebers

circadian rhythym

physiological clocks that control avian annual calendars by synchronizing internal state w/ seasonal environment

circannual cycle

synchronize to annual cycle of Earth’s revolution around the sun

photoperiod

length of daylight that triggers activity in brain, then pituitary gland that leads to cascade of activity

photorefractory period

adaptation for scheduling molt/migratory preparations during favorable conditions of late summer by discontinuing repro activity while days are still long

external coincidence model

suggests day length is measured by increased amount of time that daylight periods coincide with photosensitive phase of circadian rhythym

energetically expensive activities that separate birds temporally

breeding, molting, migrating

temporal separation in temperate vs tropical birds

temperate birds have more rigid temporal separation due to only certain times of year having favorable conditions for breeding, molting, etc. and often have to migrate

tropical birds are less likely to migrate and have more consistent conditions

natural circadian cycle w/o entrainment

pineal gland role in circadian rhythym

houses the biological clock - includes photosensitive cells, each with gene based pacemakers directing rhythmic production of melatonin

hypothalamus role in circadian rhythm

houses suprachiasmatic nuclei which are active during day and release NTs that regulate metabolic activity

effect of constant light on circadian and circannual patterns

suppresses melatonin production, can lead to insomnia, metabolic changes, impaired cognitive function

ultimate factors leading to general timing of breeding

adequate food, nest sites, locations of favorable climates, low predation risks

proximate factors

external conditions that actually induce reproduction

habitat, new vegetation, ritualized displays, neighbor aggression, social stimulation, temperature

necessary conditions that lead to species adopting migration

lack of adequate food in current habitat and severe weather

examples of long distance migrants in vt

warblers, tanagers, orioles, flycatchers, vireos

short distance/partial migrants in vt

sparrows, blackbirds, wrens

nomads

crossbills, finches, pigeons, parrots

resource predictability among long distance migrants, partial migrants, nomads

long distance: insects fluctuate predictably

partial: generalists, resources fluctuate less aggressively

nomadic: fruit, seeds fluctuate unpredictably

relative rates of productivity between temperature, tropical, and migratory species

temperate: high productivity, low adult + juvenile survival

tropical: low productivity, high adult + juvenile survival

migrant: moderate for all

Arctic Tern migration

leave nesting colonies in northern Atlantic/Arctic Ocean to go to Antartica

Red Knot migration

fly from Baffin island above Arctic Cycle to Tierra Del Fuego

Blackpoll Warbler migration

goes from New England to Antilles then to South American coasts

Bar-tailed Godwit migration

each fall they migrate nonstop from Alaska to New Zealand by draining energy reserves and muscle tissues

how are migration counts used to assess changes in migratory bird populations

“recording the numbers of birds passing specific, consistent locations—usually geographic bottlenecks—during migration seasons, acting as an index for population trends over time”

cons of migration counts

data inaccuracy via miscounting, inconsistencies per different regions

geographic relevance of Veracruz

millions of raptors and waterbirds fly past here in peak days

how is radar used for predicting migration

can be used to document when birds travel en masse in relation to continental weather patterns

why do songbirds migrate at night

use rays of setting sun as information to define departure directions

yields of metabolic water + energy generated from fat, carbs, and proteins

fat: 38.9 kj, 1.07 g water

carb: 17.8 kj, 0.55 g water

protein: 17.2 kj, 0.41 g water

polygynandry

variable type of polygamy in which males and females mate multi-fold, sometimes forming communal breeding unit

emancipation

what habitats is polygyny more common in

open habitats with clumped resources, female choice

Polygyny threshold model

“females may choose to mate polygynously when the benefits of a high-quality territory/mate outweigh the costs of sharing, compared to having a monogamous mate on a lower-quality territory”

lek

communal display grounds of promiscuous birds - aggregation of male territories with no other resources for reproduction other than opportunities to mate

cooperative breeding

‘helpers’ care for young that are not their own

could be directly enhancing their own later reproduction by ‘practicing’ or could enhance their inclusive fitness

factors leading to emancipation

development of foraging/hunting skills, avoiding predators, physical maturation, environmental characteristics

factors leading to development of polygynous and polyandrous mating systems

occurs when one sex is freed from parental care - precocial young, super abundant food, timing of fertility of opposite sex is asyncrhnous

characteristics of polyandrous species

often have reversed sexual dimorphism, high fecundity, increased male parental investment

Bicknell’s thrush and polygynandry

multiple males provide food to a single brood due to a male biased sex ratio and need for multiple caregivers in more extreme environments

polygynandrous vs promiscuous mating system

polygynandry is organized while promiscuity is indiscriminate

shell gland

adds shell colors, first as pigments deposited over course of shell’s formation, then superficial markings

albumen

egg white - mostly water and some protein. embryo’s water supply that also acts as shock absorbing cushion

makes up half or more of egg’s weight

yolk

food supply for embryo- lipids, proteins, water

ultimately absorbed into embryo

amnion

surrounds only the embryo

chorion

protective membrane that surrounds all embryonic structures

allantoic sac

sac that functions in both respiration and excretion, growing as development proceeds

air cell

source of air for chick as it starts to break out of the egg

capital breeder

species like waterfowl which draw heavily on stored energy and nutrient reserves to produce large, expensive eggs

income breeder

species that ingest resources needed for egg production on a daily basis

don’t use stored reserves despite producing an egg a day for over a month

brood patch

bare, swollen sections of skin through which birds transfer body heat to their eggs

synchronous hatching

occurs when all eggs in a clutch hatch within the same 24 hour period

asynchronous hatching

occurs due to onset of incubation before clutch of eggs is complete

creates hierarchy based on hatching order

brood reduction

accomplished by parent starting incubation before last egg is laid, promoting asynchronous hatching which leads to one of the hatchlings being weaker and thus being more likely to die rather than the whole clutch

hatching muscle

generates power for first pecks on the eggshell - withers when done

egg tooth

calcified fake tooth on tip of bill that helps chick break the shell

imprinting

occurs during critical learning period - irreversible

determines adult mate, habitat preferences

altricial

born naked, helpless

precocial

born well developed

tissue allocation hypothesis

“suggests that the high metabolic costs of a large brain are offset by reducing the size of other, similarly expensive organs—typically the digestive system (gut)—or through increased energy turnover”

interspecific vs intraspecific brood parasite

interspecifics lay eggs in nests of redheads and other duck species

intraspecifics sometimes lay extra eggs in nests of other females of same species

reproductive changes during breeding season

testes and ovaries swell

heat transfer to egg

eggs must be maintained at 37-38 degrees celsius, done via turning the egg, patches etc.

turning eggs

maintains temp of external eggs, prevents adhesion of allantoic sac to internal shell membrane that would otherwise interfere w water intake

Lack’s hypothesis on optimal clutch size

clutch size in birds is adjusted by natural selection to max # of nestlings the parents can feed and nourish

exceptions to Lack’s hypothesis

smaller clutch sizes, asynchronous hatching

relationship between age at maturity, age-specific fecundity, and annual mortality

age-specific fecundity increases in short lived species

the greater the annual adult mortality, the more short lived a species is.

age at maturity decreases in short lived species