Harpy Eagle (Harpia harpyja) nest tree selection: Selective logging in Amazon forest threatens Earth's largest eagle

Abstract

Characterizing wildlife conservation problems is essential to properly inform conservation planning, and requires detailed knowledge on critical life stages, such as reproduction. Large tropical raptors often require large emergent trees to build their huge nests. However, large emergents are also in heavy demand by the timber industry. Here, we review the literature to characterize nesting structures used by Earth's largest eagle, Harpy Eagles (Harpia harpyja) and examine to what extent nest-tree selectivity is targeted by selective logging. We show that Harpy Eagles selected specific forest canopy structures as nesting platforms. Nests were large (mean size 152 × 99 cm) and typically located on the main fork of 28 emergent tree species, 92.8% of which are commercially targeted by the timber industry. AIC-based stepwise regression indicated that, compared with non-nesting emergent trees, nest trees were 19.6% taller at the first bifurcation; had crowns 26.6% wider; had 33.3% fewer branches <45°, which were on average 35% lower-angled. Tree size varied widely across the range of nesting tree species, but peaked near the Equator, and were high-statured in unflooded forest compared with flooded forests. Our results show that commercial loggers target the same set of species and individuals on which Harpy Eagles nest, questioning whether large tracts of selectively logged Amazonian primary forests still provide suitable nesting habitat for this mega-raptor. We conclude that suitable Harpy Eagle nesting trees have been rapidly lost over the species last stronghold, and this information may prove useful to the upcoming species evaluation by IUCN.