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 (I! 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.