Density-dependent natal philopatry in southern House Wrens

Abstract

Staying or leaving the natal site is a decision that not only affects the individual but may have profound implications at the population level. Many studies have analysed natal philopatry in passerines, albeit mostly migratory species in the northern hemisphere. Here we explore the potential ecological drivers of the individual decision to remain or leave the natal site in a southern hemisphere sedentary species, the southern House Wren Troglodytes aedon bonariae. Using a 14-year database, we assessed if juvenile local recruitment was affected by demographic and/or social factors. Average annual juvenile recruitment was 18.4%, but it varied between years (range 9.3–44%), and male recruitment was higher than female recruitment. Juvenile recruitment was negatively associated with adult breeding abundance in the hatching year, but was not related to variation in adult sex ratio, adult breeding abundance in the breeding year or nesting success. Also, we found no evidence of inbreeding avoidance. The results seem to support the hypothesis that philopatry rate is regulated by intraspecific competition for resources. Juveniles that fledge in years when the density of breeding adults is low may have advantages in obtaining territories and mates early, benefiting from settling in familiar areas and reducing dispersal costs.