Fish-eating bird abundance in oligotrophic lakes in Kejimkujik National Park,Nova Scotia,Canada

Aquatic bird population data in 40 oligotrophic lakes and ponds in Nova Scotia, Canada indicates that only lakes > 20 ha support territorial pairs of Common Loon (Gavia immer) and only lakes 40 ha produce their young. Broods of Common Merganser (Mergus merganser americanus) occurred in lakes > 25 ha and loon and merganser broods together occurred only in lakes 80 ha. The fish production in the lakes was estimated from the total phosphorus vs fish yield relationship obtained in similar, oligotrophic lakes in Ontario. Considering the fish consumption and mergansers until fledging along with the maintenance of the adults during the same period (about 200 and 130 kg fish respectively) and the estimated fish production in these lakes, there is a close balance between the size of water body and its fish production to the occupancy and production of piscivorous birds.