Early environment and recruitment of black brant (Branta bernicla nigricans) into the breeding population

摘要

In geese, growth regulates survival in the first year. We examined whether early growth, which is primarily governed by environmental conditions, also affects the probability that individuals that survive their first year enter the breeding population. We used logistic regression on a sample of Black Brant (Branta bernicla nigricans) that were weighed at a known age in their first summer and observed during winter (indicating that they had survived the principal mortality period in their first year) to study whether early growth influenced the probability that those individuals would be recruited into the breeding population. We also examined the effects of cohort (1986-1996), sex, age when measured, and area where individuals were reared. The model with the lowest Akaike's Information Criterion score contained body mass, age (days) at measurement, cohort, sex, and brood-rearing area. Models that included variable mass had 85% of the cumulative model weight of the models we considered, indicating that gosling mass had a substantial effect on probability of them entering the breeding population. Females were more likely to be detected breeding than males, which is consistent with the differential fidelity of the sexes. Of individuals that survived the first year, larger goslings were more likely to become breeders. More recent cohorts were less likely to have been detected as breeders. Our findings indicate that environment during the growth period affects the ability of individuals to enter the breeding population, even after accounting for the effects of growth on survival.