Ornithology Exam 4 Super Review!

Parental care requires how many parents for raising their young?

Could be one (usually female) or both parents

Brood Parasitism

When neither parent cares for their young, they will lay their eggs in nests of other individuals (intraspecific) or species (interspecific)

Mechanism of Cooperative Breeding

Parents are assisted by relatives in caring for their young. “Helpers” are often older offspring of the parents.

Stages in Obligate Interspecific Brood Parasitism

1. Intraspecific Brood Parasitism

2. Facultative interspecific brood parasitism

3. Obligate interspecific brood parasitism

Intraspecific Brood Parasitism

Within species, leaves egg with a different individual

Facultative Interspecific Brood Parasitism

Probably interspecific parasitism of related species.

Ex) Black-billed Cuckoos and Yellow-billed Cuckoos

Obligate Interspecific Brood Parasitism

-Large clutch size

-Thick shelled eggs

-Egg mimicry

-Fast growth rate

-Removal of host eggs

-Plumage and mouth color mimicry by parasitic nestlings

Experienced Host

Have evolved inherited responses to brood parasites and experience lower levels of parasitism

Naïve Species

Have not evolved inherited responses to brood parasites and are often more vulnerable to brood parasitism.

Adaptations of Experienced Hosts

-Ability to recognize parasitic egg

-Rejection of parasitic egg

-Burial of parasitic and host eggs

-Nest abandonment

Second nesting attempts are (BLANK) to be parasitized than initial attempts

Less likely

Ecological impact of Brown-Headed Cowbird (BHCO)

BHCO originally were in the great plains, but due to humans modifying the land, BHCO invaded eastern forests and naïve species had not evolved responses to parasitism. Therefore, the reproductive success of the host species declined, as well as their populations.

In cooperative breeding, helpers can…

increase the reproductive output of the group and fitness of parents.

Cooperative breeding evolves when…

resources are scarce and unpredictable and/or when young adults are unlikely to obtain their own territories.

Territorial saturation

occurs when available territories are fully occupied, leading to increased competition for resources and potential reliance on cooperative breeding strategies.

Cooperative breeders will delay _________ to inherit the territory of an older adult

dispersal and breeding

Altruism/Kin Selection

when social groups of cooperative breeders are composed of relatives

Does the number of helpers influence female investment in reproduction?

Females will invest less in reproductions by laying smaller eggs when more helpers are present.

Clutch size and parental care represent…

evolutionary trade-off between current and future reproductive efforts

Semelparity

invest all of your energy in one large reproductive effort

Iteroparity

invest your energy in many small reproductive effort

While different avian taxa represent different stages along semelparity and iteroparity, no birds exhibit ________

obligate semelparity

Migratory passerines are….

facultatively semelparous

The Northern Royal Albatross exhibits what kind of life strategy?

“Slow Life History Strategy”

-Slow development

-Low annual fecundity

-Long life

-K-Selected species

The White Throated Sparrow exhibits what kind of life strategy?

“Fast Life History Strategy”

-rapid development

-high annual fecundity

-short life

-r-selected species

Lifetime reproductive success depends on….

Number of Reproductive Years x Annual Fecundity

The number of reproductive years depend on…

-Age at first breeding

-Potential longevity

-Age-specific mortality

Potential longevity is correlated most strongly with…

body size (larger birds will live longer than smaller birds)

The oldest known wild bird is the…

A female Laysan Albatross named Wisdom who is 74 as of February 2025 found on Midway Atoll with over 30 chicks.

Annual mortality rate is correlated with…

-body size (higher in smaller birds)

-habitat (higher in land birds than sea birds)

-latitude (higher in temperate zones)

The main causes of mortality in adult birds are…

-Starvation

-Disease

-Adverse weather

-Predation

Consider the causes of nest failure

Annual Fecundity depends on…

-Number of nesting attempts

-Clutch size

-Number of young successfully raised to fledging

Clutch Size is ____ in some taxa, but ____ in most taxa

fixed, indeterminate

Indeterminate Clutch Size

environmental conditions determine exact number of eggs, within some determinate range

Interspecific variation of clutch size is most strongly correlated with

-Latitude (smaller clutch sizes in tropics)

-Predation risk (smaller clutch sizes in open-cup nesters)

4 factors that most likely influenced clutch size evolution

-Food limitation

-Seasonality of Food Resources

-Nest Predation

-Resource Allocation

Food Limitation

-Clutch size adjusted to maximum number of nestlings that the parent or parents can successfully

-Relevance to latitudinal variation in clutch size

-Criticism: many species lay fewer eggs than they can raise

Seasonality of Food Resources

-Clutch size adjusted to seasonality of food resources

-Reproduction utilizes any and all surplus of resources above that required to maintain the adult pop.

-Criticisms: not many

how are clutch sizes affected by Nest Predation

-Clutch size adjusted to risk of predation rates

-Large clutches are more vulnerable

-Several small clutches spread the risk of nest predation

-Evidence suggests nest predation is higher in the tropics (but critics say it may not be)

Resource Allocation

-clutch size adjusted to optimal balance of resource allocation between current and future reproductive efforts

-Large clutch may reduce adult survival

-criticisms: species specific & doesn’t address latitudinal gradient

Recently extinct birds of North America

Labrador Duck
Eskimo Curlew
Great Auk
Passenger Pigeon
Carolina Parakeet
Bachman’s Warbler
Ivory-billed Woodpecker?

Audubon Societies (late 1800s)

Originally created to protect egrets and herons

National Wildlife Refuge System (1908)

Contributions of hunters to conservation; Federal Duck Stamp

Migratory Bird Treaty Act (1918)

Originally established to control market hunting
Protects non-migratory species too

Regulates hunting and trading of migratory birds across the United States and Canada.

Rachel Carson’s “Silent Spring” (1962)

Raised awareness of impact of pesticides and pollution on wildlife

Endangered Species Act (1973)

Most important legislation for protection of declining flora and fauna

Habitat loss and/or modification

creates winners and losers among wildlife and tends to favor the same winners over and over. Leads to homogenization of wildlife comunities

What you can do in your yard to support conservation

1. Reduce or eliminate the use of pesticides and herbicides
2. Plant native plants
3. Remove invasive plants
4. Attract hummingbirds with sugar water
5. Make your windows visible to prevent bird collisions
6. Leave snags and brush piles to provide cover
7. Close your blinds at night and turn off unnecessary lighting
8. Create water features in your yard

Fledging

Leaving the nest
Flying ability at time of fledging varies among taxa
Often coaxed from nest by parents’ vocalizations
Rarely return to nest once they have left

Fledgling period (food dependence and length)

Dependence on parents for food varies greatly among taxa
The length of the fledgling period varies among taxa
2 or 3 weeks is typical for many passerines
1 or 2 years for some waterfowl

Learning during fledgling period inlcudes

Foraging for food
Avoiding predators
Orientation and navigation
Integrating into social groups and dominance hierarchies
Song

Define Ecology

The study of interactions between a living organism and its environment (including other living organisms)

Define Populations

All individuals of one species in one place

Communities

A collection of populations

What is Population ecology

Understanding the mechanisms that regulate
population size

Logistic growth of population growth

Logistic growth model
Assumes that there are limits to population growth (an environmental carrying capacity = K)
Doesn’t specify nature of the limiting factors
-Food
-Nest sites
-Predators
-Etc.

Limiting factors of population growth, consider mortality rate and nest failure factors

-Adverse weather
-Habitat availability
-Territoriality
-Prey availability
-Predators, parasites, and pathogens
-Competitors

Abiotic factors

Imposed by physical environment (e.g. weather)

Biotic factors

Imposed by ecological interactions with other biological species (e.g. competition, predation)

American Kestrel:

-Females molt earlier in the season, so they arrive on wintering grounds earlier
- Females occupy the best winter territories, in open grasslands

This means…

Later-arriving males must accept less suitable winter territories in wooded or urban areas.

Interspecific competition

Occurs when two or more species compete for a shared, limiting resource (food, nest sites, etc.)

Interference competition

One species aggressively excludes other species from the resource
Direct interaction between individuals of competing species

Exploitation competition

One species depletes resources more efficiently than other species
Indirect interaction between individuals of competing species
Typically asymmetrical

Competitive exclusion

Two species with identical niches cannot coexist, because interspecific competition between the species will lead to one of two outcomes:
1) extinction of one species
2) ecological displacement (niche partitioning) shifts in distribution, habitat use, diet

Niche partitioning: Ecological displacement

shifts in distribution, habitat use, diet ecological response

Niche partitioning: Character displacement

shifts in morphology (e.g., size, especially bill size)
evolutionary response

Describe an example of ecological displacement

Five species of warblers of North American boreal forests specialize on feeding on different parts of the same trees

Give example of Character displacement

Five species of South American kingfishers have different sized bills and partition their niche based on prey size

α (alpha) richness

Number of species at a given point or site Within habitat diversity

γ (gamma) richness

Number of species in a given region Regional diversity (among many habitats)

β (beta) richness

Rate of change in species composition across sites
(habitats) Between-habitat diversity

Stability-time hypothesis

Species richness (particularly γ richness) is an equilibrium between rates of
Speciation (adds species to regional pool)
Extinction (removes species from regional pool)
Tropical regions have higher species richness because they
Have existed for a long time (promotes speciation)
Are climatically stable (reduces extinction)

Unique resources hypothesis

Tropical regions have higher species richness because of the presence of additional resources not found in the temperate zones
Or resources that aren’t abundant or constantly available in the temperate zones
E.g., fruit and nectar

Niche-partitioning hypothesis

In tropical regions
High species richness leads to intense interspecific competition
Intense interspecific competition is a selective pressure that favors specialization (narrow niches)
Specialization allows many species to “pack” into ecosystem (niche packing)