Austausch zweier ungleichaltriger Bruten des Trauerschnäppers(Muscicapa h. hypoleuca Pallas)

Summary

Five eight day old nestlings of the Pied Flycatcher(Muscicapa h. hypoleuca) were exchanged for six sixteen day old nestlings. a) The parent birds, at least the female, getting the young ones, seemed to underestimate the food requirements of the brood, their feeding frequency remaining below the value known to be normal at this age. The parents receiving the changlings nearly ready to fly, over-adjusted their feedingrate, especially the female bringing much more food than the male, wo already cared for two flown young. b) One pair fed nestlings for only 8 days, the other pair for at least 22 days. Comparison with other passerine species reveals, that in certain cases reduction of the feeding time in the nest to nearly zero has been brought about experimentally, but that the possible upper limit of this interval has not been carefully examined in either species.