An experiment on nest site choice of the Common Treecreeper in fragmented boreal forest

Abstract

Experiments in the nest site choice of breeding birds in relation to the distance from habitat edge are missing or few. We performed such an experiment with the aid ofnestbox -breeding Common Treecreepers Certhia familiaris . In their first choice of the breeding site, Treecreepers clearly favoured the boxes further away from the forest edge. In consequence, the number of successful breeding attempts was higher for the nests further away from the edge. There are two possible hypotheses to explain the results. First, the central place foraging theory predicts that a circular foraging range is optimal. The home range size of a breeding treecreeper pair is, on average, 3.3 ha, therefore, the nest of this species should be located at least 102 mfrom the forest edge in order to maintain a 3 .3 ha circular foraging area. The results agree with this expectation, because in the first choice of nesting sites 65 per cent of the nests were further than 100 mfrom the edge . Secondly, nest predation often considerably reduces thebreeding success of small passerine birds nesting nearby the forest edge. Treecreepers suffer high nest predation pressure, in particular when breeding in natural nest sites. If predation pressure is higher near the edge that may also contribute to the choice of a nest site further away from the forest edge.