Dispersal of male ortolan buntings away from areas with low female density and a severely male-biased sex ratio

摘要: Dispersal is expected to enhance individual fitness, and individuals should thus disperse from areas with poor conditions more favourable conditions. Few studies have compared before after dispersal of the same individuals, in birds little known about effects sex ratio female density on male decisions. In this study we examined various fitness-related parameters that adult ortolan buntings, Emberiza hortulana, might use as cues their decisions settle. The population has a strongly male-biased ratio. Using pairwise comparisons pre- post-dispersal conditions, found males moved low severely higher less Male age structure did not affect settlement. pre-dispersal sites was below average, but were significantly better than average. This suggests triggered by whereas settlement may been unrelated at new site. year dispersal, undertook successful acquiring remained faithful site, subsequent years there no difference. We suggest be adaptive under natural balanced These results show buntings abandon ratio, thereby end up places, although probably