An audio–visual nest monitoring system for the study and manipulation of siblicide in bearded vultures Gypaetus barbatus on the island of Crete (Greece)

Abstract

We describe here an automated surveillance system that was installed in a bearded vulture (Gypaetus barbatus) nest in Crete during 2003-2006 with the aim of studying siblicide in this species. The system caused only minimal levels of disturbance to the birds and was capable of operating autonomously for more than 1 week. It comprised (1) a nest monitoring subsystem (camera, microphone, battery with a charge controller and a transmitter together with an antenna), which was supported by a solar panel, and (2) a recording subsystem (antenna receiver, video signal controller and a remote controlled PC through a GSM modem) that compressed the audio-video signal and provided real time monitoring. Two-egg clutches with a 7-day laying and hatching interval were recorded while hatching asynchrony was also determined through an analysis of the bioacoustic data. Food delivery rate and number of feeds to the first chick increased after the hatching of its sibling although not significantly so. Of the aggressive interactions recorded, 98% were initiated by the dominant chick and resulted in an average of 246 ± 157 peckings per day. Supplementary feeding did not produce any significant correlation between feeding rate and sibling aggression. The second chick survived 5 days and died as a result of starvation accelerated by sibling aggression. Intervention measures aimed at increasing the survival chance of the second chick should be undertaken when the latter is 1-2 days old.