Patterns of predation risk and survival of bird nests in a Chilean agricultural landscape

We used experimental nests baited with California Quail (Callipepla califor nica) eggs or clay eggs to examine relative risks of nest predation in an a gricultural landscape and in two large forest preserves in a south-temperat e rainforest in Chile. The most common predators, as identified by marks on clay eggs, were a caracara (Milvago chimango), a blackbird (Curaeus curaeu s), and rodents. Nest losses from predation were similar in large and small forest patches and lower in patches than in extensive forest. In general, predation risk was higher (and nest survival therefore lower) on forest edg es than in forest interior, in short-grass pasture than in tall-grass pastu re, in narrow corridors than in wide corridors, and on visible nests than o n concealed nests. High predation risks in pasture habitat tended to increa se the risk of nest predation in adjacent forest edges. For open-cup nester s, the risk of nest predation was relatively high in the present agricultur al landscape, indicating that much of the available wooded habitat (forest edges, narrow corridors) offers poor nesting habitat, although it may be su itable for foraging and traveling. The numerous bird-plant mutualisms in th is landscape may be at risk if nesting success of the principal mutualists is consistently low.