Energy requirements of migrating Great White Pelicans Pelecanus onocrotalus

Abstract

The Great White Pelican Pelecanus anocrotalus is the largest migrating bird in Israel and is an endangered species. The Palearctic populations of the Great White Pelican breed in eastern Europe and Asia and most of them pass through the ‘bottleneck’ of Israel to wintering grounds in Africa. Natural feeding sites for pelicans have diminished during recent decades due to human activities, and sites of extensive aquaculture have become the favourite feeding places for wintering and migrating Great White Pelicans. The fish industry has reported a significant impact on fish yield and the conflict between pelicans and fishermen has escalated so that hundreds of pelicans have died in recent years from shooting or accidental electrocution. We approached this management problem by studying the energy requirements of the Great White Pelican during migration and while wintering in Israel, under different feeding regimes (fish or chicks) and in different seasons, in captivity. The results show that a captive bird consumes 1.1 kg of fish per day. The basal metabolic rate and apparent metabolized energy of the Great White Pelican are both higher than predicted from allometric equations. Energetic demands were quite stable on both diets (fish and chicks) and during both seasons (winter and summer). The fat deposits of migrating pelicans averaged 313.5 g compared with 480 g in wintering birds (3.4% and 5.4% of body mass, respectively). Based on these fat contents and on the measured daily energy consumption, we calculated that birds that do not feed in Israel can fly only up to 1620 km from Israel southward and could not cover the distance to their likely wintering grounds in the Sudd area in southern Sudan. However, birds that replenish their fuel reserves could fly up to 2460 km and hence could reach this area. Therefore, we conclude that Great White Pelicans must feed in Israel during the autumn migration in order to complete their journey to Africa. One solution to the conflict between pelicans and fishermen could be to combine deterrents preventing pelicans from feeding in fish‐ponds with the provision of attractive alternative reservoirs, to ensure regular food supplies during autumn.