Abstract
Abstract
The heterospecific attraction hypothesis suggests that migrants cue on residents with similar ecological needs to find suitable breeding sites, and that they have reproductive fitness benefits from doing so. In northern environments with low resident densities, harsh conditions and unpredictable environments, this has been shown to apply, but further south with more predictable environment and greater resident densities there has been shown both neutral and negative effect of residents on migrants. The aim of this study was to explore if migrant pied flycatchers settled in areas with a higher density of resident titmice than expected by chance, and if the flycatchers that inhabited nest boxes in high-density areas of titmice had higher breeding success than the others. The results suggests a neutral effect of the residents on the migrants; the pied flycatchers apparently settled randomly in relation to titmice, and they did not seem to have higher or lower breeding success in relation to density of neighbouring titmice. The present study area was located at an intermediate latitudinal gradient of other studies suggesting heterospecific attraction and heterospecific competition, and also had an intermediate titmice density between those studies. In the second half of the breeding period, however, the results suggests competition between the pied flycatchers and the titmice, with more pied flycatcher fledglings in low-density areas of titmice. This could be due to the cold and rainy weather in this period, which probably led to less food availability for the coexisting species in the area, which may have turned the neutral interspecific interaction to a negative one. However, there were many confounding variables in this period that may have distorted the results, like the weather, secondary mating status, and breeding phenology of titmice.