Changing patterns of nest predation and predator communities along a tropical elevation gradient

Tropical montane communities host the world’s highest beta diversity of
birds, a phenomenon usually attributed to community turnover caused by
changes in biotic and abiotic factors along elevation gradients. Yet,
empirical data on most biotic factors are lacking. Nest predation is
thought to be especially important because it appears to be common and can
change selective pressures underlying life history traits, which can alter
competitive interactions. We monitored 2,538 nests, 338 of which had known
nest predators, to evaluate if nest predation changes along a tropical
elevational gradient. We found that nest predation decreased with
elevation, reflecting the loss of lowland predators that do not tolerate
colder climates. We found different “super” nest predators at each
elevation that accounted for a high percentage of events, suggesting that
selection pressures exerted by nest predator communities may be less
diffuse than has been hypothesized, at least for birds nesting in the
understory.