Influence of habitat and number of nestlings on partial brood loss in red-cockaded woodpeckers
Partial brood loss in red-cockaded woodpeckers (Picoides borealis) was studied during 2 breeding seasons in eastern Texas. The timing of partial brood loss, group size, number of initial nestlings, number of birds fledged, and habitat characteristics of the group's cavity-tree cluster were examined for 37 woodpecker groups in loblolly- (Pinus taeda) shortleaf (P. echinata) pine habitat and 14 groups in longleaf (P palustris) pine habitat. Partial brood loss occurred slightly more in the loblolly-shortleaf pine habitat than in the longleaf pine habitat, largely because nests in loblolly-shortleaf habitat initially contained more nestlings. There was a trend for more young to be fledged by groups of 4 and 5 adult woodpeckers than by groups with only 2 or 3 adult birds. Partial brood loss was greater in nests with 4 initial nestlings than in nests with 3 or fewer nestlings. Partial brood loss was always observed in nests that initially contained 4 nestlings. When nests contained 3 nestlings, partial brood loss was significantly greater in clusters where hardwood midstory was present than in clusters where hardwood midstory was minimal, consistent with the brood reduction theory. Red-cockaded woodpeckers typically laid more eggs than they could possibly fledge young, lending support to the insurance egg hypothesis.