Habitat fragmentation reduces disperser success in juvenile nuthatches Sitta europaea: Evidence from patterns of territory establishment

We studied establishment in summer territories by first-year nuthatches Sitta europaea both in a large forest and in a set of small and isolated forest fragments (2 yr in each area). In the large forest, vacant territories were rapidly taken up by newly formed pairs of juveniles. In the fragments, settlers arrived at a slower rate, more of them remained unpaired, and more territories remained vacant at the end of the dispersal period. Furthermore, territories were taken up in a highly predictable order related to territory quality in the large forest, but not so in the fragments. We suggest that dispersal is more costly in a highly fragmented habitat, reducing the number of settlers at the population level, and reducing opportunities for pair formation and habitat selection at the individual level.