EFFECTS OF HABITAT FRAGMENTATION ON THE TIMING OF CRESTED TIT PARUS-CRISTATUS NATAL DISPERSAL

Crested Tit Parus cristatus young from first broods dispersed 1 week l ater if they were born in small isolated pine plots ('habitat fragment s') compared with individuals in a large pine forest ('continuous habi tat'). This delay in dispersal was caused by an extended period betwee n fledging and dispersal. In second broods, the delay was even longer due to the interbrood interval being 9 days longer in habitat fragment s. As nestlings in habitat fragments had a lower body-mass, and age at dispersal was negatively correlated with nestling body-mass within ea ch nest, the postponed dispersal from fragments might be explained par tly by a lower body-mass. Alternatively, postponed dispersal from frag ments could result from a barrier effect caused by reluctance to cross inhospitable habitat. Immigration by young from first broods into hab itat fragments was delayed by approximately 3 weeks, and proportionall y more second brood emigrants were recovered in this type of habitat. These results are in agreement with the hypothesis that fragments are second-choice habitat. Early immigrants into continuous habitat had a higher probability of settlement in winter flocks compared with late o nes, independent of condition or age. Therefore, Crested Tits born in habitat fragments probably have a lower chance of settling in first-ch oice habitat.