Ornithology Exam 4

Do populations of birds fluctuate?

Some are more stable than others, but all can fluctuate

What is long-term change?

bird populations can experience growth or decline over long periods of time

Life tables measure

- average age of reproduction

- average annual fecundity

- average survival of offspring

- average lifespan

Type II survivorship

consistent mortality throughout life

Leslie Matrix

Tracks the abundance or relative abundance of an age-structured population through time

Growth rate

varies based on vital stastitics

Large-bodied species

lower reproductive rates and lower over the year-over-growth potential

small-bodied species

short generation times and are able to colonize novel areas and speciate

carrying capacity

Largest number of individuals of a population that a environment can support; sigmoidal curve

Population regulation

A pattern of population growth in which one or more density-dependent factors increase population size when numbers are low and decrease population size when numbers are high.

Density-dependent factors

factor that limits a population more as population density increases

density-independent factors

limiting factor that affects all populations in similar ways, regardless of population size

population ceiling

The theoretical maximum number of individuals who can be supported by the available resources and level of technology in a geographical area.

Habitat availability

largest determination of population size

How can food supplies limit population growth?

both density-dependent and independent; too many competing for same source = dependent, crash in food resources causing mass mortality = independent

Irruptions

In addition to a population moving due to a migration, irregular (non-cyclical) migrations can occur under pressure of famine, overpopulation of a locality, or some more obscure influence.

Enemies

can limit population size (dependent & independent); can include predators, parasites, and disease

Predation

major source of annual mortality, don't always regulate populations (besides induced predators)

Parasites

large parasite loads also influence the vital rates of birds via changing investments

Disease

density dependent and independent population regulators (mosquitoes = independent, bird feeder disease = dependent)

Territoriality

limits the graphic area and habit available to individual birds, can artificially reduce carrying capacity and population growth

Stages of Habitat Occupation

1. primary habitat fills up

2. surplus birds move to suboptimal secondary habitat and wait for vacancy

3. floaters w/o territory must wait

(density dependent)

effective population size

An estimate of the size of a population based on the numbers of females and males that successfully breed (genetically diverse individuals); generally smaller than the total population.

Population bottlenecks

This happens when a population's size is reduced for at least one generation. This can greatly reduce genetic variation within the population (inbreeding depression).

founder effect

change in allele frequencies as a result of the migration of a small subgroup of a population

citizen science

scientific research by amateur scientists

What is a species?

the primary unit for describing and analyzing biological diversity

species concept

a way of defining the concept of a species and/or of providing an approach to distinguish one species from another

biological species concept

Species is a group of populations whose members have the potential to produce fertile offspring.

reproductive isolation

Separation of species or populations so that they cannot interbreed and produce fertile offspring

How is reproductive isolation maintained?

- prezygotic isolation mechanisms (sexual selection, temporal isolation, mechanical isolation [uncommon])

- post-zygotic isolation mechanisms (hybrid inferiority)

phylogenetic species concept

defines a species as the smallest group of individuals that share a common ancestor

species in practice

use independent evolutionary lineages, use both species concepts

subspecies

recognizable sub-populations of a species

Speciation

Formation of new species when a distinct species splits to become more than one distinct species

Two primary forms of speciation

- allopatric

- sympatric

allopatric speciation

The formation of new species in populations that are geographically isolated from one another. (different environments favor different attributes) (default)

sympatric speciation

The formation of new species in populations that live in the same geographic area

secondary contact

when two populations that have diverged in isolation from a common ancestor are reunited geographically

Ring species

populations that can interbreed with neighboring populations but not with populations separated by larger geographical distances

clines

the gradual changes in the frequency of an allele or trait over space (depends on the intensity of divergent selection and gene flow from natal dispersal)

static clines

there is equilibrium between selection and gene flow (composition stays the same)

dynamic clines

the composition changes with time due to ongoing diffusion of neutral traits due to gene flow or the advantage of one trait over the alternatives

Hybridization

~ 10% bird species pair with at least one other, occurs after secondary contact between allopatrically speciated pairs in hybrid zones

Hybrid Inferiority

Offspring cannot reproduce or survive as well as parent. anna's x costa's hummingbirds have ineffective courtship

Types of Hybrid Inferiority

-poor survival (hatching process/small offspring)

- poor reproductive success (intermediate courtship behaviors/infertile offspring)

Stable Hybrid Zones

a limited number of hybrid offspring continue to be produced

unstable (transient) hybrid zones

offspring are not evolutionary dead-ends, so zones can expand and move over time

Community

coexisting group of species (populations)

community dynamics

changes in species composition and interactions in an area through time

Biotic Factors

- resources

- species interaactions

Abiotic (climate) Factors

- geography

Assembly Rules

interactions determine which species occur

- colonization probability

- habitat requirements

- competitive interactions

Alpha Diversity

Species diversity at the local or community scale.

Beta diversity

the number of species that differ in occurrence between two habitats

gamma diversity

Species diversity at the regional scale; the regional species pool.

drivers of species diversity

- favorable biotic environment (biotic)

- physiological requirements (abiotic)

- accessibility to dispersal (movements)

ecological niche

A specific role of a species within an ecosystem, including its use of resources, and relationships with other species.

realized niche

the suite of characteristics it actually occupies and utilizes

types of biotic interactions

- mutualism

- predation

- competition

- commensalism

- parasitism

Top-down predation

increased populations of mesopredators hypothesized to reduce diversity

Bottom-up predation

high rates of nest predation can increase diversity

Parasitism

- little effect on community composition

- novel parasites can have more impact

competition

when one species' use or defense of a resource makes that resource less available to other species; directly influences community composition

What is resource partitioning?

Resource partitioning is when different species use different resources based on the niche space they occupy.

How does resource partitioning affect species coexistence?

Resource partitioning allows species to coexist.

What factors can impact the amount of resource partitioning?

Resource abundance and diversity can impact the amount of resource partitioning.

Does resource density = more diversity?

no, some places have extremely high density, but low diversity

Types of competition

- interference competition

- exploitative competition

interference competition

individuals interact directly with one another by physical force or intimidation

exploitative competition

competition in which individuals consume and drive down the abundance of a resource to a point that other individuals cannot persist

Habitat segregation

local separation by habitat/feeding stations is a way for species to partition resources

What happens if competition is actually restricting a species?

shift in habitat/distribution if competitor disappears (ecological release)

competitive exclusion

no two species can exist in the exact same niche at the same time

range boundaries

competition can drive distributions including abrupt range boundaries

mutualism

theoretically, mutualistic interactions between plants and avian pollinators might increase species richness through speciation

commensalism

woodpeckers creating cavities for other cavity nesting birds to nest in

species history/biogeography

individual history of a species and biogeography influences species communities (a species evolved in Australia will not live in South America despite existing niche spaces)

Island Biogeography

islands are discrete places that allow for clear examples of community dynamics and speciation

island colonizers

most species are unwilling to cross large bodies of water, so few species make it to oceanic island (except Supertramps)

mainland biogeography

older communities have more species than recent communities

Why are the tropics so diverse?

species have narrower niche breadths in the tropics --> tighter packing of species

Extinction

164 confirmed birds to be extinct in modern times

IUCN Red List

classifies species according to their risk of extinction

threats to bird populations

- habitat loss

- collisions

- hunting/pet trade

- invasive species

- pollution

- climate change

What is the most significant overall threat to birds?

Habitat loss

What activities contribute to habitat loss for birds?

Replacement of natural spaces with agriculture, mining, and development

How does habitat loss impact birds with large home ranges?

It has a strong impact on their survival and well-being

What type of birds are particularly affected by habitat loss?

Birds that rely on disturbance

collisions

- birds often fly at night and as such can collide with human infrastructure (windows/cars)

- typically compensatory

Hunting

often taken from the wild for human consumption, not an issue if regulated using science-driven decisions making

Fishing

major threat to many long-lived pelagic birds, attracted to fishing boats and baited hooks

Pet trade

significant threat to parrots, songbirds, owls, and falcons

invasive species

- largest driver of extinctions historically (particularly cats, rats, mosquitoes, and mongooses)

- predators, parasites, competitors

pollution

Farmers poisoning rodents, which are then eaten by scavengers, is a major concern for predatory birds

climate change

significant threat moving forward, especially birds in polar regions and those that occupy elevational graidents at mountain peaks

conservation biology

application of biology to counter the loss of biodiversity

population viability analysis (PVA)

A method of predicting whether or not a population will persist, gives probability of extinction and how long it will take

reserve design

process of planning and creating a nature reserve in a way that effectively accomplishes the goal of the reserve.

disturbance

regular disturbance plays an important role in habitat maintenance, especially for specialist species

- regular fire historically maintained forest dynamics

- floods have done the same for sandbars