Foraging and nesting behavior of Pallas’s fish eagle, Haliaeetus leucoryphus (Pallas, ۱۷۷۱) in the Himalayan Bhutan

Pallas’s fish eagle, Haliaeetus leucoryphus (Pallas), is listed as endangered (En) in the IUCN Red List of Threatened Species with a global population of ۲,۵۰۰ to ۹,۹۹۹ individuals. It is one of the least known species in Bhutan and assessing its foraging and nesting behavior will be one of the best conservation measures to monitor its status, ecology and conservation threats. Therefore, the nesting behavior of the eagle was observed for two months and chick feeding activities for sixteen weeks at ۲۱ vantage points along a ۷۵ km highway in the Punatshangchu River Valley, Bhutan. Fifty households residing ۵۰۰ m from the river were interviewed using structured questionnaires to examine their perception towards the eagle. A total of ۹۲% (n= ۴۶) of respondents were aware of the presence of H. leucoryphus in their locality and ۷۸% felt that it is a rare and endangered fishing eagle. However, ۸۴% (n= ۴۲) of respondents were not aware of nesting within their vicinity. The sexes of H. leucoryphus can be differentiated by their plumage and the fledgling was observed approximately one week after the end of the incubation period. It took ۱۱۲ days for the fledging to leave the nest. The study revealed that the eagle preferred foraging between ۷  and ۹ AM in the morning and in the afternoon from ۱ to ۳ PM. The maximum foraging attempts occurred in a pool habitat ۵۴% (n= ۳۷) with a success rate of ۷۸% (n= ۵۴). The hunting and feeding of the fledgling was done by the male and prey delivery in the first two months consisted of ۷۸.۵% fish and ۱۹.۵% rodents. However, the feeding of fish declined by ۳۵% in the next two months and its diet mainly consisted of small birds. Attacks on the fledgling were done by the crested serpent eagle (Spilornis cheela Latham) (۴۸%), followed by the black eagle Ictinaetus malaiensis (Temminck) (۳۳%).

Keywords:

Conservation threats , diet , eagles , endangered , fledge , prey , sexual dimorphism