Behavioral Adjustments of Cuckoo Nestlings (Cuculus Canorus) to Foster Parents

The behavior and adjustments of a cuckoo nestling developing in a redstart nest were studied. High acoustic sensitivity was found in the range of non-species-typical components of the sonic feeding complex of the host species. The general tendency of avian hearing development, accelerated formation of low-frequency range, also plays an important role in the biology of the parasite species. A constantly increased level of feeding motivation along with the high acoustic sensitivity are basic for the 100% responsiveness to arrivals of adults with food. Vocalization matching, that is, a coincidence of the frequency band limits and of the intensity of vocalization of a cuckoo chick and redstart brood ensures the equal frequency of feedings. The coincidence of sequence and timing of the periods of nest life of cuckoo and redstart young that were determined with respect to the change of the modality stimulating feeding behavior increases the feeding competition abilities of a cuckoo nestling in the case of forced coexistence with the young of the host species

Behavioral Adjustments of Cuckoo Nestlings ( Cuculus Canorus ) to Foster Parents

The behavior and adjustments of a cuckoo nestling developing in a redstart nest were studied. High acoustic sensitivity was found in the range of non-species-typical components of the sonic feeding complex of the host species. The general tendency of avian hearing development, accelerated formation of low-frequency range, also plays an important role in the biology of the parasite species. A constantly increased level of feeding motivation along with the high acoustic sensitivity are basic for the 100% responsiveness to arrivals of adults with food. Vocalization matching, that is, a coincidence of the frequency band limits and of the intensity of vocalization of a cuckoo chick and redstart brood ensures the equal frequency of feedings. The coincidence of sequence and timing of the periods of nest life of cuckoo and redstart young that were determined with respect to the change of the modality stimulating feeding behavior increases the feeding competition abilities of a cuckoo nestling in the case of forced coexistence with the young of the host species

Stimuli for nestling begging in blue tits : hungry nestlings are less discriminating.

In altricial birds, nestlings usually respond to the sound and appearance of the provisioning adults by begging for food when the adults arrive at the nest. Nestlings can, however, also beg incorrectly on hearing misleading sounds in the environment and fail to beg when the adult arrives. This study uses the blue tit Cyanistes caeruleus to test the hypotheses that nestling begging strategies are influenced by the reliability of the stimulus to beg, and that nestling motivational state affects the response to different stimuli. Here, we show experimentally that nestling hunger strongly influences the response to stimuli that vary in their reliability. While hunger increases begging rate, it also increases the likelihood that nestlings will beg when the parent is absent. This is in agreement with both the predictions of signal detection theory and recent empirical work on other species. We found, however, no evidence that age-related perceptual constraints influence the begging response of ten day old nestlings to different stimuli