Psychobiological Aspects of the Acceleration of Postembryonic Development in the Asynchronous Breeder, Pied Flycatcher ( Ficedula Hypoleuca )
Abstract
The nest behavior of the pied flycatcher nestlings was studied in the artificially formed broods. Each of two groups of nestlings with an age range of four days were studied. Under optimal food conditions, the last of the nestlings to appear shortened the incubation period by 20-25% so that the whole brood fledged relatively synchronously. During the first half of nest life in the mixed broods younger nestlings got food mainly due to their constant motor activity, manifested in unceasing spontaneous begging, resulting from the constantly increased level of feeding motivation. During the second half of the nest life younger nestlings, due to their high activity level, get even the greater amount of food than the elder chicks. The long-lasting contact of the nestlings of both age groups is necessary for the selectively accelerated development of sensory and motor components of functional systems of early behavior that ensure the survival of younger nestlings and their fledging, synchronous with the older ones. It is suggested that all factors promoting the accelerated development of younger nestlings are present in the natural habitat.