Enhanced predation rates on cavity bird nests at deciduous forest edges-an experimental study

Abstract

The size of a forest tract influences the composition of the fauna. If forests become fragmented this will affect the fauna in several ways. One of the main effects is enhanced nest predation. Several studies which confirm this effect have been carried out, but none has used natural cavities . I tested experimentally whether the predation rate was higher in natural tree-holes close to the forest/farmland edge than in the interior ofthe wood. In a fragmented deciduous forest, fresh Quail eggs were placed in natural cavities at various distances from the edge. The eggs were exposed during a period corresponding in length to the egg and nestling period of a hole-nesting bird . In the beginning of the period, the predation rate was higher close to the edge (< 20 m) than further inside the wood. This result may indicate that a predator first searches the ecotone and afterwards penetrates deeper inside the forest . The results is in accord with earlier observations that nests in natural cavities seem to be less vulnerable than other types of nests .