General Life History of Birds

1. General Life History of Birds • Higher mortality in first year, lower constant mortality therafter • Most vulnerable in nest, juvenile period • Long-lived • Breed multiple times, relatively low investment in each breeding attempt • Small number of young with large investment in each

2. Low end: temperate passerines • Begin breeding age 1 • Lifespan 3-5 years • High reproductive effort (large clutches) • Driven high mortality birds migrate, winter in cold climates

3. High end: seabirds, parrots • Begin breeding age 9-10 • Lifespan 50 years or more • Low reproductive effort (small clutches)

4. Intermediate: gulls, tropical birds • Begin breeding age 2-4 • Lifespan 10-20 years • Intermediate reproductive effort

5. Survival Rates

6. Age Effects on Reproduction • Improvement over first 2 or 3 ages of reproduction common • Due to improving foraging skills, ability to compete for resources, mates • Delayed breeding linked to improved success with age • Best not to attempt reproduction if cannot be successful

7. Delayed Breeding • Occurs in monogamous species in which foraging skills improve greatly with age (gulls, jays, seabirds) • Males, but not females delay in resource defense polygyny (Red-winged Blackbird) and lek systems (manakins) • High cost if attempt to breed too early: 75% mortality in female Adelie Penguins that first attempt to breed at age 3 rather 4-5

8. American Redstart males get adult plumage at age 2, but breed in low quality habitat at age 1: avoid competition with older males

9. Dispersal • Females disperse more often, farther than males in most bird species • Opposite pattern in mammals • Males sedentary due to advantage in competition for resources, females move to avoid inbreeding • Mortality of females is higher than that of males due to mortality costs of dispersal

10. Red-cockaded Woodpeckers

11. Higher mortality in 1st year • Female mortality > male mortality (1st year, adults) • More dispersal by females (1st year, adults) • Males stay to control resources, females move to avoid inbreeding

12. Costs of Inbreeding • Viability of eggs: hatching rate of eggs reduced 13% in inbred pairs • Viability of young: survival of fledglings to age 1 year reduced 29% in inbred pairs

13. Cost of dispersal: mortality plotted against % of survivors that disperse, for breeding females in different situations, ranging from (E) son inheriting territory (nearly all disperse) to (A) mate survives and reproduction is successful (almost all stay). Mortality of those who stay (left intercept) is projected as 26%, mortality of dispersers (right intercept) is projected as 59%.

14. Mortality as a function of age • Higher mortality 1st year, then constant • High mortality at oldest ages

15. Reproductive success as a function of age • Improves through age 5 (6Y), then constant • Lower at oldest ages in females

16. Senescence • Decline in function (weight, survival, reproductive success) in old age • Occurs in RCWs, other species too

17. Fledglings (clear bars) and yearlings (dark bars) produced by 2-year old breeding males with and without helping experience do not differ, in both pairs (2) and pairs with one helper (3)

18. Age Effects on Reproduction • Lack of helpers reduces success young birds • Experience feeding young (as helper) does not matter, but experience as a breeder does • May reflect value of experience with mate, coordination of activities • Improve with age regardless of presence of helpers or breeding experience • Probably due to improved foraging skill