Vocal Activity of Little Bittern (Ixobrychus m. minutus) during the Breeding Season

Abstract. Heron vocalization and its behavioral functions are one of the least researched aspects of heron biology. The main aim of this study was to investigate the patterns of seasonal and daily vocal output of male Little Bittern (Ixobrychus m. minutus; n = 8) during the breeding season (May–August). The advertising call started on 10th May, and finished on 28th July. The first peak of calling activity occurred between 21st May and 1st June, and the second one was between 14th June and 7th July. The daily vocal activity fluctuated and depended on the time of day. The males were most active between 0300–0900 hours and 1600–2200 hours, with the highest peaks in vocal output occurring before sunrise and before sunset. Higher vocal activity was observed in the evening compared to the morning hours. Moreover, the vocal activity of males was not related to air temperature.