Inbreeding depression and its effects on natal dispersal in Red-cockaded Woodpeckers

Natal dispersal is a key life-history component that may be influenced by t he fitness consequences of inbreeding. We studied natal dispersal and inbre eding within a large population of cooperatively breeding, endangered Red-c ockaded Woodpeckers (Picoides borealis). We assessed the costs of close inb reeding, the spatial distribution of related males and its relationship to dispersal distance of females, and the change in dispersal behavior of fema les in the presence of closely related males. Close inbreeding resulted in a significant loss of fitness, through two separate effects: closely relate d pairs (kinship coefficient greater than or equal to 0.125) exhibited lowe red hatching rates and lowered survival and recruitment of fledglings relat ive to unrelated pairs. Despite a highly predictable spatial clustering of closely related males near the female's natal territory, natal dispersal di stance of females was not sufficient to avoid these males as mates. Females changed dispersal behavior in the presence of closely related males on the natal territory: female fledglings were significantly more likely to dispe rse from natal territories if there were closely related males breeding the re in the following year. Females did not change dispersal behavior in the presence of related males that were not on the natal territory. We suggest that dispersal behavior is a trade-off between benefits of shea-distance di spersal, e.g., an advantage in competing for scarce breeding vacancies, and the substantial cost of close inbreeding.