The Osprey (Pandion haliaetus), with a nearly worldwide breeding distribution and a tolerance for both fresh and salt water, feeds almost exclusively (99+%) on fih (Grove et al. 2009). The availability of prey is an important factor inflencing its productivity (Van daele and Van daele 1982, harmata et al. 2007). Time spent on foraging is a function of prey availability, and success in breeding may be related to food provisioning (dykstra 1995) as well as the food supply (croxall et al. 1988). Under favorable conditions, provisioning rates are elevated, and birds fully meet their own energetic requirements and those of their chicks (cairns 1987, Weimerskirch 1998). Proximate causes of nest failure include bad weather, avian and nonavian competitors, and predation, as well as insuffiient care by inexperienced parents. if
the weather is bad, the adults may be unable to forage (hudson 1985). however, the ultimate cause of nest failure may often be food shortage (Steenhof and Newton 2007); for example, a female unable to provision her chicks abandons her brood, which is then vulnerable to predation.