Longer breeding dispersal than natal dispersal in the ortolan bunting

Abstract

Theoretical models dealing with dispersal patterns are currently limited by a lack of empirical data, and existing data may be biased because of small spatial scale of many previous studies. We studied the whole known population of a small passerine bird, the ortolan bunting (Emberiza hortulana), in Norway. Males conducted extraordinary long-distance breeding dispersal of up to 45 km during their first years of life but showed high territory fidelity when older. Males that failed to attract a female in their first singing territory were especially likely to disperse, and their movements regularly occurred within a breeding season or until the next year (such movements were also defined as breeding dispersal). Breeding dispersal distances of males (median ¼ 11.9 km) were more than four times as long as their natal dispersal distances (median ¼ 2.7 km). These data contradict a classical view of dispersal in birds, namely, that the longest dispersal movements occur before the first territory is established (natal dispersal) and subsequent movements (breeding dispersal) are shorter. Thus, breeding dispersal plays a larger role than does natal dispersal in gene flow and population connectivity in the ortolan bunting. We suggest that short natal dispersal and subsequent long breeding dispersal within the breeding season may be an optimal dispersal strategy in ortolan buntings owing to their patchy distribution in our study area, and we predict that this may also be the case for other species with patchy or fragmented distribution. Key words: breeding dispersal, Emberiza hortulana, natal dispersal, ortolan bunting, territory switching. [Behav Ecol]