Population ecology and behaviour of the Osprey Pandion Haliaetus (L.) in eastern Nova Scotia

A study of the population ecology of ospreys Pandion haliaetus (L.) was conducted in Antigonish County, Nova Scotia between 9 May and 22 August, 1978. An activity time budget was recorded for eight nesting pairs, four of which nested an average of 3.0 km from Pomquet estuary while another four were located an average of 11.5 km inland from Antigonish estuary. The time budget of the mated pairs revealed a division of labour between the sexes. The primary interest of the females centered upon the nest and its contents. That of the males were directed towards obtaining food for himself, his mate and offspring. Ospreys employed two breeding strategies. The coastal nesters foraged for winter flounders Pseudopleuronectus americanus (Walbaum) in nearby estuaries while the inland birds fished lakes and streams for white suckers Catostomus commersonei (Lacepede) , but mostly for gaspereaux Alosa pseudoharengus (Wilson) and blueback herring A. aestivalis (Mitchill). Once the Alosa spp. have spawned and returned to the sea, the inland nesters shift their foraging locations to the estuary, an average round trip distance of 23.0 km. This compares with an average foraging distance of 2.3 km before the shift. Not only does this shift increase foraging time dramatically but the birds now took a smaller fish, the flounder. However, both these coastal and inland ospreys fledged approximately the same number of young/pair. Intra-and interspecific behaviours of ospreys were also described.