Natural nest sites of the Collared Flycatcher Ficedula albicollis in lime-hornbeam-oak stands of a primeval forest

Abstract

Knowledge of habitat and nest site selection of secondary hole nesting birds under primeval conditions may aid in managing forests and in conservation biology. We studied location (n = 768) and dimensions (n = 624) of Collared Flycatcher nests in natural tree holes in a lime-hornbeam-oak stand of the Białowieża National Park, Poland. Collared Flycatchers bred most often in hombeam Carpinus betulus, in holes that were on average 8.1 m above the ground in trees of a mean diameter at breast height (DBH) of 43 cm. The majority of nest holes were situated in tree trunks (79%), with most of these (87.9%) in living trees. Nest holes were either originally made by woodpeckers (17.4%), or created by natural decaying processes. The minimum diameter measurement of the entrance hole for all Collared Flycatcher nests was 4.6 cm on average. The average distance between the outer rim of the entrance hole and the floor of the nest cavity (danger distance) was 25 cm. The median floor area of the nest cavity was 96 cm2. Differences between orientations of the hole entrances were insignificant.