Molt and nest overlapping in long-distant migrants: main regularities of plumage replacement in the pied flycatcher, Ficedula hypoleuca (Passeriformes, Muscicapidae), from Karelia [Russian]

摘要

The studies of Ficedula hypoleuca in southern Karelia (1979-2002) showed that the time of beginning of molting and nesting and frequency of their overlapping in bird populations varied markedly between years. A complex of external factors correcting the endogenic program of postnuptial molt related to specific features of a season was detected. These factors include breeding time, clutch and brood sizes and weather conditions in spring and summer. The molting of males depended on the environmental conditions to a greater extent that that in females. Probably, these birds are capable to change the time and rate of molting depending on seasonal environmental conditions. This circumstance allows the birds to combine molting and nesting without an increase in their energy expenses, damage to themselves, their mate and offspring. The overlapping of molting and breeding is suggested to be an adaptation of birds for the maximal use of resources during the most favorable season of a year.