Group Size and Nest Success in Red-cockaded Woodpeckers in the West Gulf Coastal Plain: Helpers Make a Difference.

We studied the relationships between Red-cockaded Woodpecker (Picoides borealis) group size and nest productivity. Red-cockaded Woodpecker group size was positively correlated with fledging success. Although the relationships between woodpecker group size and nest productivity measures were not statistically significant, a pattern of increasing clutch size and number of hatchlings with increasing group size was apparent. The presence of helpers appeared to enhance the survival of nestlings between hatching and fledging. The contribution that helpers make to nestling feeding and incubation, cavity excavation, and territory defense appears to have a positive effect on nest productivity. A threshold number of helpers may be necessary before a significant benefit for fledging success is realized. Nests with four and five group members fledged more young than nests with two or three group members. Whether partial brood loss occurred or not within a nest was primarily a function of clutch size and the number of hatchlings. Although partial brood loss did affect the number of young fledged from individual nests by removing young from nests with high numbers of hatchlings, woodpecker group size appeared to be the primary determinant of fledging success