Plasticity of nest-site selection in the trumpeter finch: A comparison betweentwo different habitats

摘要

In habitats with more predators, a species is expected to breed in safer sites and be less successful than inpredator-impoverished habitats. We tested this hypothesis by studying nest-habitat selection and nestpredation in two populations of Trumpeter finch (Bucanetes githagineus). One breeds in a predator-richhabitat (Tabernas, Iberian Peninsula), and the other is found on an island with fewer predators (La Oliva,Canary Islands). In both localities, we studied the features of nests in two different substrates, on theground and in cliffs, including visibility and position in the cliff. We measured the habitat characteristicsin a series of plots around the ground nests and compared them to random points. We also studied theinfluence of nest features and habitat selection on predation of both nest types. Trumpeter finches builtmore nests in cliffs in Tabernas, probably because there are more cliffs available there. In this locality, thepatches selected for ground nesting had below-average vegetation cover, lower vegetation height, andwere on steeper slopes. In La Oliva, they selected above-average vegetation height and steeper slopes.Cliff nests were less predated than ground nests in La Oliva, but not in Tabernas. The only variable thataffected survival rates in Tabernas was the height of vegetation around ground nests, with nests in lowervegetation having higher survival rates. These results suggest that locality-related differences in habitatselection by vegetation height could be related to the different predator assemblages present in any givenarea, though we cannot rule out confounding influences of other differences between the two sites.