IB 461 Exam 3

Natural Selection

organisms that are more adapted to their environment are more likely to survive and pass on their successful genes

Lifetime reproductive success

- the number of fledged offspring during your lifetime

- the number of offspring that survive to adulthood

- the number of grandbirds you produce

- determined by survival and breeding

Avian life histories

- set of evolved traits or attributes

- combines behavior, ecology, population biology, and evolution

Life history patterns

- relative performance determines strategy advantages/disadvantages

- tradeoffs between longevity and reproduction

Principle of allocation

the observation that when resources are devoted to one body structure, physiological function, or behavior, they cannot be allotted to another

Bird longevity and lifespan

- live 1.5 to 2.5 times longer than mammals

- lifespan 2-5 years

- birds live longer in captivity

- track lifespan from bird banding

Cormack-Jolly-Seber model

Estimate apparent survival and recapture probability in open populations (where individuals can enter or leave the population between sampling events)

Bird survival rates

- 30% to >95%

- large > small

- seabirds > landbirds

- tropical > temperate

- older > younger

- Males > females

- summer > breeding

- territory > migration

- risk of death during winter and migration

Migration mortality

- 85% mortality

- monthly mortality risk 15 times greater

Age-specific mortality

- variation between age classes

- juvenile survival about 50% of adult survival

- 17% die in first week compared to <0.5%

- adult survival essentially constant

Sex-specific survivorship

- females tend to have higher mortality (higher cost of reproduction; more likely to be predated while incubating)

Fecundity

- number of young raised successfully

- annual fecundity determined by number of nesting attempts, nest success, number of broods, and clutch size

- influenced by age/experience of breeders and habitat

Nest attempts

- number of attempts per season dependent on length of breeding season and availability of resources

- predation followed by female nest rebuilding

Nest Predation

- colonial nesting species will sometimes lose entire populations

- predation risk may limit brood size in both precocial and altricial species

- more young may increase predation risk (longer egg-laying period, more noise, increased visitation by parents, risk fewer eggs and renest frequently)

Attempts

total number of nesting attempts

Broods

number of successful attempts

Tropical vs temperate species broods

- tropical species have more broods than temperate species

- more re-nesting in tropics

-long nesting cycles

- restricted breeding seasons reduce repeat attempts

short-lived species

- make more attempts

- lower probability of another opportunity

Clutch size

- number of eggs laid in a nesting attempt

- precocial species lay up to 20 eggs

- passerines lay 2-6 eggs (up to 19 eggs)

- cavity nesters lay more eggs than open cup

Increases in clutch size with latitude hypotheses

- increased day length allows more foraging

- seasonality thins population and decreases competition for food during breeding season

Lack's food limitation hypothesis

clutch size in birds is adjusted by natural selection to the maximum number of nestlings the parents can feed and noursih

Trade-off between long- and short-term gains

Integrates the maximization of reproductive effort with the probability of survival and energy needed to raise later broods

Predation hypothesis

Birds in areas with high predation may want to produce smaller clutches due to the risks associated with predation (time to lay and incubate more eggs, more young and nosier, and risk fewer eggs)

Parasitism assurance

some birds may lay a fixed number of eggs and can therefore know if there is one more egg in the nest that the nest has been parasitized and they should eject of abandon

Seasonality hypothesis

clutch size is related to the resources avaliable

Clutch sizes compared

Temperate > tropics Highlands > Lowlands Cavity > Open cup

Small species > Large species

Mainland > Island

Precocial > Altricial

Age and experience egg production trade-offs

- first time breeders produced fewer eggs

- egg production increases with age followed by reproductive senescence

age-specific reproductive sucess

based on age-specific experience, effort and progressive disappearance of phenotypes due to variation in individual productivity and survival

Delayed Maturation

- some species wait a few years breed

- parrots 2-3yrs, raptors 3-4yrs, seabirds > 4 yrs, albatrosses 8-12 yrs

- delayed breeding favored when early breeding unsuccessful

- age at maturity decreases with increasing annual adult mortality

Survival and Reproduction balance

- adult survival decreases as reproductive investment increases

- fecundity increases as reproductive investment increases

- fecundity curve levels off because of diminished investment returns

Song Sparrow life-history pattern

- short life

- early breeding

- many attempts in a year

- produces 3-5 young for a few years

Wandering Albatross life-history pattern

- long life

- 8-11 years before breeding

- breeding produces 1 chick every 2 years

Life tables

- describe patterns of survival and fecundity

- based on females

- age of first reproduction can have huge contribution to LRS

Sx

annual survival of an age (proportion surviving)

Lx

survivorship, probability of survival to a given age

Bx

average number of young per female

LxBx

expected annual fecundity of an individual bird

How to calculate Lx

- look at the fledglings Sx and Lx number

- for adults 1, multiply Sx from fledglings by the Lx of the fledglings

- for adults 2, multiply Sx from adults 1 by the Lx of adults 1

How to calculate the the LxBx

- for adults 1, multiple the Lx by the Bx

R0 and life tables

- add up all the LxBx to get R0

- R0 = 1.0 --> stable

- R0 > 1.0 --> increasing (1.5 means 50% increase)

- R0 < 1.0 --> declining

Population

- collection of individuals from the same species within a defined area

- often fuzzy (boundaries poorly defined), political boundaries, based on discrete habitat patches

Population ecology

study of how intraspecific (within same species) and interspecific (among species) interactions among individuals and interactions between individuals and the environment affect the abundance and distribution of a species

Population trends

- often enumerated to allow for comparison

- rarely stable or static

- over time can trend down or hold steady

- overall increasing

- annual variation caused by winter food limitation

Population declines

- overall bird population declining

- trends show decline great declines in grassland, arctic tundra and western forest

Bird growth potential

- 100-120 european starlings released in 1890

- by 1940 there were 120 million starlings

- Cattle egrets colonized in North America in the 1950s

- increased by 2000x by 1971

General bird population trends

-populations increases followed by periods of stability

- all populations are in a state of flux

- more bird species are declining then increasing

BIDE model

- a model of 4 factors that can change population's distribution or abundance

- births, deaths, immigration emigration

Birth + immigration > death + emigration

- increasing populations

- common species

Birth + immigration < death + emigration

- decreasing populations

- rare species

4 principal ecological factors that influence bird populations

- habitat

- food supply

- disease

- climate

habitat

- place where an organisms naturally occurs, lives and grows

- provided food, predator protection, shelter, a place to build and attend to a nest, a place to raise juveniles and essential ingredients to enhance individuals fitness

All purpose habitat

- everything needed is within one general area

- tropical and temperate resident species

Specific use habitats

- necessary ingredients for fitness may be separated by non-suitable

- migratory species, and species with more complex lifestyles

- stopover habitat during migration

Habitat generalists

- flexible in habitat use

- widely distributed

- abundant

Habitat specialists

- constrained in habitat use

- narrow distribution

- scarce

Types of habitats

- grassland

- shrubland

- forest

- wetland

- pelagic

- urban

Critical habitat under Endangered Species Act

- specific geographic areas essential to conservation of threatened/endangered species

- may include areas not currently occupied by species if they are deemed essential

- focus on physical or biological features needed for life processes (breeding, feeding, sheltering, migration)

Purpose and implications of Critical Habitat

- helps prioritize conservation efforts and recovery planning

- triggers federal consultation to avoid habitat destruction or degradation

- often controversial due to land use conflicts and perceived regulatory burdens

- studies show positive impacts on species recovery, though effectiveness varies

The Endangered Species Act

- prohibits the "take" of species listed as endangered

- "take" = to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, orcollect, or attempt to engage in such conduct

Food

- most foods don't want to be eaten

- exceptions: fruit, nectar

Food in tropics

- most abundant birds are frugivores

- plants dispersed by birds

- birds eat pulp from fruit and pass seeds

- foraging adaptations --> reach and grab or "sally-glean"

food in temperate regions

96% of North American birds use insects for nestling caterpillars

Avain flu

- H5N1 --> bird to bird transmission

- detected in 12,000 wild birds

- waterfowl natural carrier

Population limitation

any ceiling on population growth

Population regulation

- average size of population depends on population density

- determined by birth and death rates

- determined by immigration and emigration

Effects of density on population

- population size can be determined by density-dependent and density-independent factors

- under ideal conditions λ > 1 for all populations

- λ --> population growth

Density independent growth

- density-independent factors

- effects on birth and death rates are independent of number of individuals in the population

ex: temperature and precipitation, catastrophes, floods, hurricanes

Density dependent growth

- Density-dependent factors --> Birth,death, and dispersal rates change as the density of the population changes.

- As density increases, birth rates often decrease, death rates increase, and dispersal (emigration) increases, all of which tend to decrease population size

Bird population regulation

- density dependent factors cause population to increase when density is low and decrease when density is high

- when food, space and other resources are in short supply and population size decreases

Density dependence in births

- effects fecundity

- number of pairs increases, clutch size decreases

- as number of pairs increases, broods decrease

- as number of pairs increases, number of young fledged per pair decreases and levels off at about 4

- density increases, vital rate decreases

- reproductive output related to limits to biomass and resources

Population regulation in deaths

- death increase as density

- mechanisms --> starvation (food limitation), diseases (transmission increases), predation (prey switching)

Density dependence in movement

- immigration decreases as density increases

- emigration increases as density increases

Allee effect

at low densities, individuals have difficulty finding mates, or defending colony, so reproductive rate decreases as population density decreases

Emergent properties of a population

- age structure

- spatial structure

- source-sink populations

- meta-populations

Age structure

the proportion of the population in each age class

Ideal free distribution

- Individuals will distribute themselves among patches in a manner that reduces competition and maximizes fitness

Ideal Despotic Distribution

- Territorial, aggressive individuals occupy best habitats, subordinates forced into lesser habitats

- older birds most often found in best habitat and territories

Source populations

- Enough offspring produced to not only offset adult and juvenile mortality, but also send offspring off to new areas

- Births > Deaths

- Emigration > Immigration

Sink populations

- Not enough offspring produced to offset adult and juvenile mortality

- Deaths > Births

- Immigration > Emigration

Source-Sink Equation

λ = Pop yr1 / Pop yr2

λ = PA + (PJ )(R)

λ

- proportional change in population from one year to the next

- > 1 is growth

- = is unchanged

- < 1 is decreases

PA

the probability an adult survives from one year to the next

PJ

the probability a juvenile survives from one year to the next

R

reproduction (number of female offspring per breeding female per year)

Edge effects reduce nesting sucess

as distance to edge increases, proportion of nests decreases

Species distribution patterns depend on...

- physical environment

- distribution of resources

- dispersal

- competition

Patterns of geographic distribution - global scales

- at large spatial scales all show aggregation or clumping

- environmental and ecological constraints determined aggregation and range extent

- abiotic conditions at one edge biotic on another

Dispersion

the pattern of spacing among individuals within the boundaries of the population

Patterns of species distribution - regional/local scale

- degree to which of subpopulations are isolated depends on distance between subpopulations, nature of intervening environment, mobility of the species

- clumped, random and uniform

Clumped distribution

- individuals in discrete groups

- may arise from social predisposition to form groups, clumped distribution of resources, and tendency of progeny to remain near parent

Random distribution

- individuals distributed independently of others within a homogenous area

- may arise from neutral interactions between individuals, neutral interactions between environment and equal probability of persisting anywhere

Uniform distribution

- individuals maintain a minimum distance from other individuals

- may arise from direct interactions among individuals with minimum distance between individuals or direct competition for limited resources may cause pattern

census

a complete count of individuals in a population

index

a qualitative measure

estimate

made on the basis of a statistical sample

Christmas bird count

- helps measure population growth

- takes volunteers

- started in 1900, 90 species and 18,500 individuals

- 2021 --> 65 groups in illinois

- document irruptive species

- increases in hummingbirds and warblers

Breeding bird survey

- Quantifiable data on migratory birds

- Started 1965.

- US and Canada

- Count all birds heard

- Experts only

- helps create distribution and change maps

eBIRD

- Online platform for bird observation data collection

- began in 2002

- 2 billion observations

- rare occurrences

Estimating abundance stuggles

- detecting is an issue with all surveys

- all observers aren't created equal

Lincoln-Peterson Estimator

N = n(K)/k

N--> number of ducks in population

n --> number of ducks marked in visit 1

K --> number of ducks captured in visit 2

k --> number of marked ducks recaptured