Feather selection and replacement patterns demonstrate that Goldfinches Carduelis carduelis fix postjuvenile moult extent prior to moult initiation

Abstract

Birds undergoing a partial moult have to make important decisions regarding moult extent, pattern and sequence. Moreover, since partial moults are usually subject to a great degree of individual variability, the mechanisms controlling and organising such moults can be particularly complex. In the present paper, I investigate the feather selection and replacement process involved in partial postjuvenile moult in the Goldfinch Carduelis carduelis. Moult patterns observed after moult completion indicate that birds select the feathers to be replaced according to a predetermined order of moult priorities. However, the sequence of feather replacement, both within and between feather tracts, differs markedly from this order of moult priorities, varying individually to be adjusted to the final moult extent. These results indicate that, prior to or at the beginning of moult, each bird fixes with precision which feathers will be replaced. These findings have important implications for the interpretation of partial and incomplete moult patterns and for our understanding of the underlying factors controlling moults.