ИСТИНА

Using video recording of Pied Flycatchers, which reared chicks at the age of 9-13 days, we evaluated their feeding rates (FR) and number and size of preys in each delivered food portion. Male colour type was estimated by Drost’s 7-step scale. Unlike many other avian species with monocyclic breeding, the considerable proportion of pied flycatchers overlaps two energy-consuming productive processes, breeding and moult. FR was negatively related to mean size of food portion. Moulting males visited their broods less often than non-moulting ones. This relation was more pronounced in pale males (V-VII morphs by Drost’s scale) than in conspicuous males (II-III). FR was negatively related to the strength of experimentally induced humoral immune response, and this relation also tended to be more pronounced in pale males. As we have showed earlier, namely during moult pale males demonstrated stronger immune response than conspicuous males. Moulting pale males heightened the antibody titer after immunization, while moulting conspicuous males tended to reduce the strength of immune response. Non-moulting males of different colour types showed the same immune responses. The results on feeding behaviour of Pied Flycatchers suggest that pale males mounting immune response during moulting period, face critical physiological constraints that could be avoided by lowering such energy-consuming activity as FR.