Ornithology Lec Final Chp. 19 - Life History Strategies

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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

The White Throated Sparrow exhibits what kind of life strategy?

“Fast Life History Strategy”

-rapid development

-high annual fecundity

-short life

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…

Laysan Albatross

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

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 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 teh 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

Nest Predation

-clutch size adjusted to risk of predation rates

-large clutches are more vulnerable

-several small clutches spread risk of nest predation

-nest predation higher in 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