African fish eagles (Haliaeetus vocifer) and marabou storks (Leptoptilos crumeniferus) in Uganda: Use as biomonitors of environmental contamination

A study was designed to evaluate concentrations of persistent organic pollutants and mercury in African fish eagles (Haliaeetus vocifer), marabou storks (Leptoptilos crumeniferus) and tilapia fish (Oreochromis niloticus) in Uganda. Total mercury concentration in breast feathers; plasma concentrations of a range of persistent organic pollutants; packed cell volume and plasma chemistry values were determined for adult and nestling African fish eagles at Lake Mburo (n = 18) and Lake Victoria near Entebbe (n = 15), as well as marabou stork nestlings in Kampala (n = 21). Morphometric measurements were collected on adult fish eagles. A human and eagle food, Oreochromis niloticus were sampled for total body mercury and a range of persistent organic pollutants (n = 18). Feather mercury concentrations were significantly (p ≤ 0.05) lower in fish eagles at Lake Mburo than fish eagles from Entebbe and marabou storks from Kampala. Five adult fish eagles and five Oreochromis niloticus from Entebbe had concentrations of 4,4′-DDE of less than 0.005 ppm wet weight in plasma and fish samples. The research establishes concentrations of these pollutants in these species and allows future trend analysis. African fish eagles and marabou storks meet many criteria of a suitable avian biomonitor of environmental pollution. With appropriate development, long-term research and integration with other monitoring initiatives, these species could become valuable tools to assess environmental change.