Non-Random Philopatry of Sibling Spotted Sandpipers Actitis macularia

Philopatry data from a long-term study of Spotted Sandpipers were used to test the hypothesis that yearling returns were independent, and to evaluate explanations for non-random return. Full siblings from the same nest returned more frequently than expected if returns were random. Sibling philopatry was not related to fledgling production, fledging success, brood size, parental identity, or fledging date. Sib yearlings did not return to the breeding grounds together. Data were consistent with the explanation that sib fledglings remain associated for some portion of their first year. There are two major impacts of non-random sibling return. First, when coupled with the high philopatry of both sexes and the high breeding site fidelity we have observed in previous studies, non-random return of young siblings further increases the potential for inbreeding. Second, these results illustrate the importance of testing behavioral assumptions about independent dispersal or philopatry in other species, such as in analyses of density-dependent philopatry or dispersal distance heritability.