Ornithology 3

behavior

any internally coordinated, externally visible pattern of activity that responds to changing external or internal conditions

• response to stimulus (internal stimulus=hormones; external stimulus)

experience

learned behavior

inheritance (genetic factors)

innate behavior

innate behavior (instinct)

inherited via genetic information

serving to perform specific functions (survival and reproduction)

closely related species tend to show similar behaviors to accomplish certain goals

nature vs nurture controversy

• nature; don’t need to “learn” behaviors

• mobbing behavior-gang up on a predator (even unrelated/different species)

fixed action patterns

fixed action patterns

→stereotyped, species specific behaviors elicited by specific stimuli called sign stimuli or releasers

Niko Tinbergen

everyone in the population has the trait to perform an action pattern in response to stimulus

once stimulus starts, action pattern must be completed, even if stimulus is removed halfway through

EX: greylag goose sees egg outside of nest and rolls it back

learned behavior

adaptive modification of behavior by experience

Konrad Lorenz

types:

• imprinting

• habituation

• conditioned behavior

• trial and error learning

• insight learning

imprinting

learning that occurs only during a restricted time period called the critical learning period

imprint on nest style/habitat type, know who parent is, etc.

habituation

learning not to respond to meaningless stimuli

begins as a reduction of response because stimulus ends up meaningless

dear enemy hypothesis

dear enemy hypothesis

birds declaring territory, new bird takes territory next to it, immediately first bird squares up, eventually both realize that they’ve each got their own boundaries and won’t mess with each other

conditioned behavior

involves attaching a pre-existing response to a new or substitute stimulus

classical

operant

classical conditioned behavior

pavlovian

existing response paired with a new stimulus

operant conditioned behavior

skinner

more trial and error-like, chooses behavior based on reward/punishment

trial and error learning

involves modifying response to stimuli or creating new responses

learning curve

learning curve

decline in error over time

insight learning

production of new response upon reorganization of experience

“spontaneous problem solving”

may use experience in other situations and apply it to new problem

used for enrichment in captivity

communication

process in which a specialized signal produced by one individual affects the behavior of another

signaler

signal receiver

signaler

individual that produces a signal (auditory, visual, chemical)

signal receiver

individual that detects a signal

sensory receptors-nerve endings molecules attach to/react to air vibrations/pick up light

• chemoreceptors: pick up chemicals in air/water/substrate-olfaction, gustation. conspecifics/pheromones

vocalizations

a few birds lack a syrinx and therefore have no “voice”

• capable of croaks and grunts (vultures)

most birds produce the voice with the specialized avian organ: the syrinx

• tracheal, bronchial, tracheobronchial

• produce different notes from each side, close/open more, make 2 different sounds at the same time

2 types: songs and calls

• range from simple, single notes to complex combination of sounds-including 2 “voices” at the same time

locality information

recognition

song repertoires

mimicry

vocalization advantages/disadvantages

advantages:

• quickly modify vocalizations depending on environment (alert others to predators)

disadvantages

• degrade farther away

• can’t really dodge obstacles

songs

relatively long and complex vocal displays with specific repeated patterns

• pair bonding: attract mate/improve bond

• territory maintenance: declare territory

• reproductive isolation: important between species with same morphology to distinguish each other

calls

short simple vocalizations

• enemy avoidance/warn others

• flight calls (short calls in flight)

• flock/contact calls (flock bonding)

• parent-young relations

  • which food to eat

  • keep in close contact

locality information in bird vocalizations

short notes with broad frequency range

• direction and distance (mobbing calls, assembly calls)

faint, high pitched, narrow frequency range, and long duration

• conceals location (alarm calls)

low frequency sounds

• carry over long distances (owls hoot)

amplitude/size of wave (loudness) and frequency (pitch) are both important in bird communication

vocalizations recognition

species recognition

a single species may have several different dialects

many songs are the result of learned behavior, while others are innate

4 stages of learning song repertoires

individual recognition

stages of learning song repertoires

critical learning period

• listening and storing information during birds first year; dendrites forming in brain (important for lifelong learning)

silent period

• processing stored information, dendrites forming in brain

subsong period

• notes produced, but often in wrong sequence

song crystallization

• notes put into correct order and timing

• can find mates and defend territory now

vocalization species recognition

accomplished by acoustical structure of song and sometimes syntax (repetition of syllables, etc.)

single species may have several dialects

vocalization individual recognition

accomplished via details of pitch, phase structure, syntax, and composition of calls and/or songs

→slight variations in individuals

song repertoires

the number of different types of song that an individual is capable of singing

more songs=more impressive to females

• better genes/characters, better territory/resources

large repertoires may increase male reproductive success

mimicry

→imitating calls or songs of other species

lyre bird

potential purposes of mimicry

hypotheses, but nobody really knows

may be involved in excluding competing species from the mimic’s territory (if they share resources or something)

may assist in calling other species to mob predators

visual communication

photoreceptors: rods (low light) & cones (color vision)

visual communication advantages and disadvantages

advantages:

• much quicker recieving (detect visual signals much quicker/instantly)

disadvantages

• attract enemy

• requires clear skies/water, no fog; you have to be able to SEE

• needs light

visual communication functions

territorial defense

attraction/courtship of a mate

maintenance of bonds (flocks)

• dominance hierarchies in social animals

many birds have distinctive and colorful markings

plumage

• color, elaborations of it: lyrebird/peacock tail, crests, hoods

color

patterns

bill coloration/color around bill

face/eye ring/leg/foot coloration

some species exhibit distinctive sexual dimorphism, age specific plumage differences, and seasonal plumage differences

males and females look different

juveniles have different plumage than adults

plumage drab in winter, vibrant during breeding season

related to need for communication

camoflauge

plumage differences important for:

species recognition

• slight differences between closely related species

individual recognition

• slight individual differences in coloration

• way to communicate dominance in social species

social status

• harris’s sparrow males: darker throat=higher dominance. lots of variation in the bib(some have almost none vs all the way down breast)

courtship displays

designed to attract a member of the opposite sex

usually males attracting females and/or pair bonding (already a pair)

may involve ritualized activities

may occur in common on a Lek

may involve elaborate display of inanimate objects

may be related to specific part of the anatomy

courtship displays may involve ritualized activities

activities may serve other functions

tidbitting

intention movements

mock threats

can escalate into fighting (usually males)

tidbitting

mother shows chicks which food item to forage/where to forage/how to forage

intention movements

usually male-male defining territory lines

posturing, calling

courtship displays may occur in common on a Lek

en masse

gathering of a bunch of males, each with his own spot, females choose (hypothesized either “hot shot” or “hot spot”-best male or best nesting area)

prairie chickens

courtship displays may involve elaborate display of inanimate objects

bowerbirds

decorate “bower” (not nest) with things, sometimes even with particular color/color scheme which can sometimes include plastic

• interior design is his passion

courtship displays may be related to a specific part of the anatomy

tail

• long-tailed widowbird females prefer males with long tails

• peacocks

• lyrebirds

visual communication can be very complex

great blue heron

• EX: stretch, wing preen, landing calls, bill duel, tail alert

• one display type can be used in multiple ways

antagonistic displays

displays used to intimidate or manipulate another bird (usually male-male)

showing plumage (dominance), calling, crests, etc/

means of resolving conflict without direct contact, reducing risk of energy

dietary characteristics range from omnivorous to highly specific

granivory (seeds)

insectivory (insects)

carnivory (meat)

herbivory (vegetation/foliage)

nectivory (nectar)

piscivory (fish)

frugivory (fruit)

food choice involves lots of factors

familiarity

learned behaviors

competition (other species or same species)

obtainability

nutrients (calorie intake vs cost to acquire it)

foraging specialties

many birds show learning with respect to feeding

examples:

• great tits on the british isles opening milk bottles

• green herons using bait to lure minnows

• woodpecker finch using sticks to pry out grubs

• egyptian vultures cracking ostrich eggs with stone

• finches moving rocks to uncover food

optimal foraging theory

→benefits must outweigh costs

behaviors that maximize fitness

involves “decisions” about”

1. what foods to eat

2. where to feed

3. search paths to follow

4. when to change foraging sites

what foods to eat

maximize reward intake per time

• profitability of food items (profit=benefits/cost)

• number of food types available

• deciding which items to eat

  • specialists (good at searching/handling specific food) vs generalists (broad spectrum of food items)

  • may change seasonally

• handling time (how long does it take to manipulate and swallow food)

predictions for what food bird will eat

a bird should specialize on most profitable items and occasionally choose less profitable, but never choose Only less profitable

the switch from generalizing to specializing should be sudden

“decision” to specialize depends only on availability of most profitable item

zero-one rule (scale from never eat this food item to always eat this food item)

empirical evidence of optimal foraging theory

laboratory:

(krebs et al. 1977, 1978)

great tits chose both large and small mealworms equally when in low supply, but preferentially chose large when both were common

field evidence of optimal foraging theory

davies 1977

insectivore eats insect of varying sizes and profitability

(figures on slides-J/s units)

optimal patch use model

when to switch sites?

theoretical predictions

• a bird should move when the rate of food intake in a patch falls to a level equal to the average for the habitat as a whole

diminishing returns

• longer time spent eating food time/foraging in a patch, the more the cumulative energy gain diminishes

how far away are food patches? travel time to new patch?

laboratory evidence (cowie 1977)

• conclusions: birds behaved as if they were optimizing energy intake

inconsistencies and problems with optimal patch use and foraging theory

birds do not always behave as if foraging optimally. various factors may prevent them from foraging optimally (predation, competition, dominance hierarchies, morphological constraints)

it is also very difficult to precisely define the reward around which birds optimize (energy or specific nutrients)

birds will sometimes visit low yield sites repeatedly or feed on inferior food when better “choices” are available. Why?

• perhaps to monitor future foraging opportunities in case present conditions change

some account for roundtrip (feeding young, caching, divers taking a breath)

foraging for young

foraging for young (optimal foraging theory)

optimization of the load for parents bringing food back to the nest for the young

prediction:

• birds should carry heavier loads if travel time between patch and nest is increased

assumption:

• energy gain decreases as load size increases (ie prey becomes difficult to handle)

• bryant and tatner (1982): house martins load increased as travel time increased, although predicted loads and observed loads were not in particularly close agreement

learning to feed

young birds must learn:

• what to eat

• how to stalk prey

• correct method for obtaining prey

• how to handle prey

strong learning curve based on experience (trial and error learning)

prey items provided by parents readily eaten on their own

those not previously encountered treated with caution

food caching

uncommon in avian species

exceptions:

• acorn woodpecker (tons of acorns in tree holes)

• shrikes (stab prey on thorns")

• some raptors

• tit mice

fat reserves

generally low (might put on more before migration, less than 10% total body weight)

small birds have proportionally less fat

• warbler: TBW=20g, 1 day survival on fat at 5C

• kestrel: 200g, 5 days

• emperor penguin: 40kg, 90 days (lose 45% of body mass)

torpor can increase length of time an individual can depend on fat reserves

types of pair bonds

monogamy

polygamy

• polygyny

• polyandry

• polygynandry

• promiscuity

monogamy

1 male, 1 female

both care for young

extra pair copulation very common

polygyny

1 male, multiple females

common

1 male defends territory, multiple females nest within it.

female cares for young

polyandry

multiple males, 1 female

male cares for young

female may defend territory or not, males have nests

sequential polyandry

polygynandry

multiple males, multiple females

social bonding (multiple bonds)

no more than one parent caring for young

promiscuity

multiple males, multiple females

no pair bonding

no more than one caring for young

extra-pair copulations

both male and females

many “monogamous” species found to have multiple paternity

due to “forced copulation” by neighboring males

cuckoldry

• males raising offspring of other males

• not all eggs in one basket

mallards:

• can be groups of bachelor males with no pair bonds

• often with injury or death to female

Egg content

Embryo or ova (if un fertilized)

Yolk-nutrient supply, shrinks as embryo develops

Albumen-main protein for protection; “egg white”

Blastoderm-outer cellular layer that forms the blastula pre-embryonic/early development

Extra-embryonic membranes

Extra-embryonic membranes

Amnion

Chorion

Allantois

Yolk sac

Amnion

Immediately surrounds embryo

Chorion

Contains embryo, yolk, allantoic sac

Allantois

Allantoic sac, for respiration and excretion

Yolk sac

Vitelline membrane; membrane over the yolk

Shell structure

Inner fibrous shell membranes

Eggshell composition

Thickness of shell

Shell texture

Pores

Inner fibrous shell membranes

The ones that are there when you’re trying to peel a hard boiled egg

Isthmus

Eggshell composition

Uterus

CaCO3 (calcium carbonate), Mg2+ (magnesium), phosphates

Network of collagen-like fibers

Thick cuticle layer, palisade layer, and layer that interfaces membranes

Thickness of shell

Controlled by uterus and palisade layer

Depends on health of bird

Shell texture

Cuticle (very thin, mostly protein, full of air bubbles)

• proteins have anti-microbial function

Pores

Holes in egg shell

Gas exchange

Egg coloration and shape

Pigments

Egg color is mostly determined genetically, but other factors apply

Coloration thought to have evolved as a means of concealment

Egg shape

Pigments determining egg color

2 main pigments responsible for egg color

1. Porphyrins-derived from hemoglobin (brown and olive colors)

2. Cyanin-derived from bile (blue and green colors)

May occur singly, together, or not at all

May occur in different layers, or penetrate the entire shell

White is probably the primitive color (no pigments)

Pigments secreted by pigment glands in the uterus

Egg color is mostly determined genetically, but other factors apply:

Streaking due to erratic movement of the egg during pigmentation

Spots resulting from no movement during pigmentation

Albino eggs (egg moved too quickly, or pigment glands non-functional)

Erythrism: reddish eggs laid in response to red substrates (ground nesters in red clay area)

Age specific coloration

Coloration thought to have evolved as a means of concealment

Evidence: most cavity nesters lay white eggs

• most birds that incubate immediately lay white eggs

• Open nesting birds that cover the eggs with down or vegetation lay white eggs

• Bare ground nesters have different colored/patterned eggs on different substrates

Egg shape acquired while in the ______ of the oviduct

Magnum

• diameter determined by muscular tension of the oviduct walls

• Actual shape is associated with the shape of the pelvis

• Shape of no real importance in most cases

Egg shape of no real importance in most cases EXCEPT:

Pyriform (pear shaped) eggs of shore birds and other ground/cliff nesters

Pointed at one end and tend to roll in small circles

Kiwi: egg is 25% of body weight (most birds like 4-11%)

Clutch size

Heritable trait-why such variation?

Varies by altricial vs precocial species

Altricial species

Young hatch naked, blind, helpless

Precocial species

Young hatch feathered and self supporting

Evolution of clutch size

4 major hypotheses (assuming that natural acts to optimize clutch size):

1. Lacks hypothesis

2. Trade off hypothesis

3. Predation hypothesis

4. Seasonality hypothesis

Lack’s hypothesis

Food limitation

Supported by experimentally increasing/decreasing food (food down=clutch size down)

Trade off hypothesis

Lifetime reproduction bs annual reproduction

Trade offs affect long term reproduction of an individual

Depends on life history

Go all in on a clutch, risk shortening lifespan→smaller clutch=longer life=more eggs overall

Predation hypothesis

Predation of 1st egg

Larger clutches take longer to lay → more time being vulnerable, especially if they don’t incubate all at once

Larger clutches noisy

Produce smaller clutches

Seasonality hypothesis

Resources and clutch size tracking resources

Food availability happens in a wave-like pattern as different insects hatch and emerge

Non-migrating species

Resources at breeding set clutch size that particular season or clutch (resources of 2nd clutch different than 1st)

Incubation

2 patterns of incubation are present in birds:

1. Incubate as soon as first egg is laid

2. Incubate after clutch is complete

Incubate as soon as first egg is laid

Typically precocial

Result in hatching asynchrony

Why lay >1 egg if resources aren’t available for >1 offspring?

• insurance in case 1st egg or offspring dies

• Adaptive in species faced with irregular or unpredictable food supply

Incubate only after clutch is complete

Typically altricial

Result in hatching synchrony

Allows immediate switch from incubation to care of young

Care of young

Amount of time and energy devoted to parental care varies depending on whether the species is altricial or precocial (spectrum)

Spectrum of maturity hatching

• precocial still has a lot of investment, just in egg making rather than after hatching

Hormonal influence

• prolactin

• Males decrease testosterone and increase prolactin

Brood parasitism

Involves laying eggs in nests of another species (host) then abandoning them to the care of the foster parents

Practiced by: old world cuckoos, new world cuckoos, cowbirds, honeyguides (Africa), whydahs (Africa), black-headed duck (South America), parasitic weaver (tropical Africa), coots, and many others

Advantages to brood parasitism

Relieves parasites from many of the costs of reproduction

Allows them to lay more eggs per breeding season

Increases their potential reproductive fitness

Coots and brood parasitism

Coots parasitize other coots nests

Count eggs to keep track of their own, recognize by color, time of laying, etc

Might kill invader, kick it out, move it to inferior incubation spot, bury it and build another nest on top of it

Earlier laid eggs succeed better→ sneak more eggs that will hatch sooner into more empty competitor nest (more likely to be detected)

How did brood parasitism evolve?

2 scenarios for the evolution of brood parasitism have been proposed:

1. Avoidance of nest competition

2. Intraspecific brood parasitism→facultative parasitism evolves→expanded repertoire of hosts and loss of making own nests