Species-Specific Nest Selection by Birds in Ant-Acacia Trees

Abstract

We examined nest site differences among four bird species nesting in acacia (Acacia collinsi) trees with ants that may deter nest predators at Palo Verde, Costa Rica. Rufous-naped Wrens (Campylorhynchus rufinucha) showed a non-random preference for nesting in trees with unusually active ant colonies. They nested most commonly in trees with the most active ant species (Pseudomyrmex spinicola and P. nigrocinctus); and, when they nested in trees with a less active species of ant (P. flavicornis), these trees usually contained colonies that were more active than the average for their species. Other bird species (Streak-backed Oriole, Icterus sclateri; Yellow-olive Flycatcher, Tolmomyias sulphurescens; Great Kiskadee, Pitangus sulphuratus) used trees for nests at random with respect to ant species and consequently these ants were much less active than ants on Rufous-naped Wren nest trees. We found no differences among bird species in tree size, local acacia density, or degree of nest isolation. Nest predation on eggs in artificial nests was higher in acacia than non-acacias due to pecking by Rufous-naped Wrens, suggesting that wrens may be inhibiting other bird species from nesting in the most protected nest sites.