Philopatry, Site Fidelity, Dispersal, and Survival of Spotted Sandpipers

Abstract

We assessed philopatry, site fidelity, dispersal, and survival during the last eight years of an 18-year study of Spotted Sandpipers (Actitis macularia). The first 10 years of the study were of an island population. For the last eight years of the study, we expanded the study area to include a mainland subpopulation, 7 km from the primary island population. We also assessed between-site movement. Yearlings made up 7 to 36% of breeders recruited annually, and yearling return was negatively associated with number of fledglings the pre3;2;­ vious year. We found male-biased philopatry when all yearling returns were included, but no significant sex bias of birds that returned and bred. Return rate for males that successfully bred was 63%; for males that were not successful, 29% returned. For females, the return rate of successful breeders was 63% and for unsuccessful breeders 26%. Females changed territories between clutches more often after nest failure, and birds moved more often to the island than to the mainland. We used hatch and fledging success, philopatry, and site fidelity rates to construct male and female life tables, separating successful and unsuccessful breeders. From U.S. Fish and Wildlife Service recovery records, dispersal distances ranged from 3.6 to 147 km. We conclude that expanding our study site gave a more accurate picture of philopatry, dispersal, and site fidelity. Birds apparently treated all study areas as a single site, with the island preferred to the mainland for breeding.