Juvenile survival and recruitment of wood thrushes Hylocichla mustelina in a forest fragment

Abstract

We tested if juvenile survival and recruitment (returning to breed) of wood thrushes Hylocichla mustelina into their natal population was dependent on several measures of nestling condition, growth, and site fidelity. Overall, nestling mass, wing chord, condition, and rank within the brood did not affect the probability of survival to the post‐fledging stage, independence, or recruitment. We did not identify any morphometric differences among nestlings that remained in the study area after fledging and those that did not (or those that did not survive). Time of season and the number of days nestlings were present in the study area after hatching, or site fidelity, were the only variables measured that positively influenced juvenile survival and recruitment. Based on a restricted sample, fledglings that eventually recruited did not differ in size during post‐fledging or post‐independence from fledglings that did not return to breed. Independent, immigrant hatching‐year (HY) birds are briefly described. Overall, immigrant HY birds had a higher probability of recruitment than all local fledglings. There was no difference in the probability of recruitment between immigrant HY birds and independent local fledglings (those present ≥35 days after hatching), however. Similar to local young, the number of days present in the study area increased the likelihood of recruitment for immigrant HY birds, although these effects could not be distinguished from those of emigration or survival.