TOLERANCE TO HABITAT FRAGMENTATION INFLUENCES THE COLONIZATION OF NEWHABITAT BY FOREST BIRDS

We examined the relationship between the ability of bird species to pe rsist in fragmented forests and their ability to colonize new forest h abitat. Using a long-term darn set on the colonization of a forest pla ntation, we tested the hypothesis that bird species tolerant to habita t fragmentation would detect and colonize the new habitat faster than intolerant species. The forest plantation under study is situated on a n area of land reclaimed from the sea (a polder) in the central part o f The Netherlands. We constructed an index of tolerance to habitat fra gmentation and included it as a predictor variable in a set of three l ogistic regression models that compared the probability of colonizatio n over four consecutive time periods. After controlling statistically for the effects of regional incidence, preferred habitat and life-hist ory characteristics, there was a significant effect of tolerance to fr agmentation on the ability of species to colonize the plantation, and a marginal effect on the timing of colonization. We then examined the effect of the same index of tolerance to fragmentation on colonization patterns over a larger spatial scale. Multivariate regression models showed that the proportion of three polders of different ages occupied by forest bird species was dependent upon the regional incidence of a species, its preferred habitat and its tolerance to fragmentation. Th e results support the hypothesis that species tolerant to habitat frag mentation detect and colonize new habitat faster than those intolerant to habitat fragmentation.