Influence of forest management on pre- and post-fledging productivity of a Neotropical migratory songbird in a highly fragmented landscape

Abstract

Little is known about the effects of forest management on fledgling survival in birds, despite the fact that this is a key determinant of overall productivity. In 2005–2006, we compared male density, nesting success, and fledgling survival of Hooded Warblers (Wilsonia citrina Boddaert, 1783) among forest fragments that were reference sites (n = 3; not logged in >21 years) or had received either a standard selection system harvest (n = 3) or a heavy cut (n = 5) within the past 6–10 years. Density tended to be higher in logged sites than reference sites, but cumulative probability of nest survival (0.22 ± 0.02; 21 days) did not differ among treatments. Brown-headed Cowbird (Molothrus ater (Boddaert, 1783)) parasitism was significantly higher in recently logged sites, and reference sites produced significantly more Hooded Warbler young per successful nest than standard selection harvest sites. Logging treatment did not have a strong negative effect on fledgling survival, and overall, 51% (33/65) of fledglings survived until three weeks after fledging. Standard selection harvest sites had the highest Hooded Warbler density (0.2 males/ha) but also the lowest seasonal productivity (0.84 independent fledglings/female), raising the possibility of an ecological trap. The estimated number of daughters produced per female per year that are expected to survive to breeding age was lower for all treatments (reference, 0.26; selection, 0.17; heavy cut, 0.32) than the expected annual mortality probability of adult females (0.4–0.6). Forest fragments in this region appear to be population sinks, regardless of extent of partial harvest within the fragment.