Ornithology - Exam 3

Frequency

Cycles/second (Hertz or Hz). Perceived as pitch.

Amplitude

Relative intensity of the sound, measured in decibels.

Wavelength

Distance (in meters) traveled by one cycle (period).

Greatest frequency range known in a single song

Brown-headed Cowbird

Reverberation

“echo” - multiple reflections of sound; “blurs” sound

Amplitude fluctuation

Passage of sound through turbulence

Lombard Effect

Unconscious increase of vocal output in response to background noise, including speaking louder and higher pitches

Infrasound

Very low-frequency sound

Elephants, giraffes, some whales

Only one bird species known to hear and produce infrasound

Functions of Song

Territory defense

Mate guarding

Resource competition

Coordinating parental care

Paid bond maintenance

How does song develop?

Sensitive period (memorization phase)

Involves:

Acquisition - song learned

Storage - song retained in memory

Sensorimotor (or motor) phase

Period during which bird begins to produce song

Subsong

Soft, unstructured, random sounds (baby babbling)

Plastic song

Correct elements, still somewhat unstructured

Crystallized song

Final adult song

Duets

Synchronized vocal displays, mostly between mates

Mate guarding

Territory defense

Pair bond maintenance

Allopreening

Social grooming behavior between pairs and flocks

Advantages of Higher Rank

Desirable perches

Food access

Residency times

Reduced predation

Interspecific interactions

long-term or temporary relationships between individuals of different species within a community

Social Mimicry

Subordinate species may mimic the plumage of dominant species to minimize aggression

May also include vocal mimicry

Flocks

Can be single or mixed species

Can be temporary or long term

Scroungers

Don’t look for food patches, wait for producers to find them

Source Population

Produces excess young that disperse to another breeding population

Sink Population

Cannot sustain themselves except through immigration

Life Tables

Summary statistics for age-specific survivorship and fecundity

Limitation

Upper limit to population growth (density-independent)

• habitat, food, climate, disease, predation

Regulation

Effects of population density on population size (density-dependent)

• ex: Great tits lay fewer eggs when population size is higher

Limiting Factors: Habitat

Very specific habitat needs make birds more vulnerable to habitat loss

Availability of nest sites (like tree holes) limits population size

Many conservation efforts are habitat focused

Limiting Factors: Food

Drought or hard winters can cause density-independent losses

Ocean temp changes can change food availability for seabirds

Irruptions

Irruptions

Large scale influx of birds into an area outside their normal range

Limiting Factors: Other Organisms

Predators - natural source of mortality, can have larger effects if introduced

Parasites - worms, ticks, blood parasites, blowflies, botflies

Diseases - bird flu, west nile

Floaters

Non-territorial birds whose movements overlap with established territories

Presence of floaters =

Habitat is saturated with breeding individuals

Bottlenecks

After population crash - can lead to bottleneck (reduced population size, low genetic diversity)

Inbreeding

Often leads to hatching failure

Value of Long Term Monitoring

Insights into population trends

Bird banding stations

Christmas Bird Count

Breeding Bird Survey

eBird

Species

The result of common ancestry and descent

Forms a reproductive community (gene flow)

Shares a similar ecological niche

Practice assortative mating (like mates with like)

Allopatric Speciation

Geographical separation that interrupts gene flow

Sympatric Speciation

No physical separation, but other mechanisms of reproductive isolation

Breeding System

Pattern of mating and parental care behavior in a species

Inclusive Fitness

An individuals total genetic contribution to the next generation

Extra-pair mating

Mating outside the primary social pair bond, increasing genetic diversity

Influences on Systems

Food availability, nesting site distribution, parental care requirements, competition

Clumped resources

Polygyny

Uniform resources

Monogamy or polyandry

Monogamy

One male and one female form a pair, shared parental care, high offspring survival

Polygamy

One or both sexes have multiple mating partners, reduced parental care per offspring, increased mating opportunities

Polygyny

One male mates with multiple females

Occurs when females can raise offspring alone

Resource Defense Polygyny

Males defend territories rich in resources to attract females

Female Defense Polygyny

Males directly guard multiple females

Lek Polygyny

Males gather and display in a shared area (lek), and females choose mates based on their performance

Polyandry

One female mates with multiple males

Occurs when males can raise offspring alone and resources are abundant

Sex-Role Reversal

Males provide parental care

Females compete

Cooperative Polyandry

Multiple males help care for the same brood

Sequential Polyandry

Males incubate the first clutch and then the female will incubate the second

Polygynandry

Multiple males and multiple females mate with each other within a group

Results in uncertain paternity and shared parental care

Dunnocks

Flexible breeding system dependent on environmental conditions

Influenced by food abundance and territory size

Brood Parasitism

A reproductive strategy in which a bird lays its egg in the nest of another individual, relying on that host to raise its offspring

Cooperative Breeding

Individuals other than the parents help raise offspring

Kin Selection

A form of natural selection where individuals increase their fitness by helping relatives reproduce

Reciprocal Altruism

Cooperation where individuals help each other with the expectation of future benefits

Complex Family Structure

A social system involving extended family groups with multiple related individuals and participating in breeding and care

Rely on individual recognition and long-term memory

Same-Sex Pairings

A pair bond formed between two individuals of the same sex that may involve nesting and parental care

Nest Functions

Protection

Microclimate buffering

Concealment

Sanitation

Parasite control

Fecal Sacs

Many passerines package nestling waste for removal or consumption to reduce disease

Medicinal Architecture

Adding aromatic plants to nests as fumigants against bacteria and mites

Prolactin

Incubation and parental motivation

Testosterone

Inversely correlated with paternal care

Corticosterone

Stress hormone; elevated levels can reduce or reallocate parental effort under food storage

Tropics

Longer breeding seasons, smaller clutches, extended parental care and learning

Temperate

Seasonal food peaks, larger clutches, intense provisioning during short windows

Polar/Arctic

Extreme seasonality - synchronized breeding and rapid chick growth

Hybrid Zones

Regions where previously isolated species come into contact with one another

Reinforcement

If the hybrids are MORE fit, or high degrees of gene flow

Fusion (two species become one)

Hybridization occurs often but both species remain intact

Population Viability Analysis (PVA)

Uses age structure, population growth, mating system, environmental changes and spatial distribution of animals to model population viability