Szymon Marian Drobniak , Agnieszka Gudowska

Moult is a process, usually occurring annually, in which birds replace their plumage. It is one of the most crucial life-history traits because it restores the functions of plumage and allows a bird to adapt to environmental conditions or special seasonal needs such as breeding and camouflage during non-breeding season. Consequently, moulting has advantages in terms of future performance. However, it also has immediate costs related to producing protein-rich tissue, reduced thermoregulation and flight performance. Expression of such costs may depend on a wide array of physiological and environmental factors experienced by an individual. Considering a variety of factors affecting moult dynamics in single studies, we use a systematic meta-analytical approach to summarise existing evidence and look for general patterns in how moult depends on both extrinsic (environment, ecological variability) and intrinsic (physiology, energy reserves, life stage) factors.