Sex biased natal dispersal is not a fixed trait in a stable population of Seychelles warblers

We observed a change in the sex-specific rate of delayed natal dispersal in a stable population of Seychelles warblers over a period of 20 years. At first, females were more likely to delay dispersal in their first year of life than were males, whereas later there was no sex bias in the rate of delayed natal dispersal. Similarly, the female-bias in helping-at-the-nest and the male-bias in floating have also weakened over time. These changes may have resulted from the decrease in variation in territory quality observed in the population over the study period. Our findings strengthen the view that natal dispersal is a highly plastic response to local ecological and social circumstances, and clearly show that rates of sex-biased dispersal cannot be considered a species or population constant. Our study also highlights the importance of collecting long-term datasets to understand complex behaviour such as natal dispersal.