Meeting Abstract

44.3  Sunday, Jan. 5 11:00  Nestling growth rate and juvenile survival MANESS, TJ*; ANDERSON, DJ; Louisiana Tech University; Wake Forest University tmaness@latech.edu

The survival probability of birds during the juvenile period, between the end of parental care and adulthood, is highly variable and has a major effect on population dynamics and parental fitness. As such, a large number of studies have attempted to evaluate potential predictors of juvenile survival in birds, especially predictors related to parental care. The hypothesis linking body reserves accumulated from parental care to the survival of näive juveniles has organized much of this research, but a variety of other predictors have also been investigated and received some support. We used path analysis to test potential predictors of juvenile survival of 2631 offspring from seven annual cohorts of a seabird, the Nazca Booby (Sula granti). Fledging age was the most important predictor of juvenile survival: fast-growing offspring survived best, when all other variables were held constant. Offspring sex was the next most important predictor, with juvenile males (the smaller sex) surviving better than females did. Hatching day, an index of body weight, and wing length also showed important predictive ability, but cohort size, culmen length, and an index of clutch size and hatching success did not. Nestling growth was compromised under poor rearing conditions: overall weight fell, the number of days needed to reach fledging status increased, and growth of some structures, but not others, were reduced. These effects were more pronounced in females, and the higher juvenile mortality of females accounts for most of the male bias in the adult sex ratio and its attendant “mate rotation” mating system in this population.