Female characteristics and breeding success of the collared flycatcher Ficedula albicollis [Temm., 1815] in natural forest [Bialowieza Forest, East Poland]

The relation between Collared Flycatcher females’ selected characteristics (age, body condition and wing length) and breeding success was studied during seven breeding seasons (1995–2001) in nest-boxes in old-growth oak-lime-hornbeam of Białowieża Forest (Eastern Poland). Yearling females started laying almost three days later and produced smaller clutches (6.1 vs. 6.4 eggs) with fewer nestlings (5.4 vs. 6.1) and fledglings (5.1 vs. 5.7) than did older females. No differences were found in partial losses (i.e. proportion of eggs or nestlings that did not fledge). Body condition had influence only on time of egg laying. Wing length of young females was positively correlated with number of fledglings but no relations were found with other reproductive parameters. Age may be a key factor influencing breeding success in female Collared Flycatchers in the natural conditions in Białowieża Forest.