Abundance and distribution of fish-eating birds in Kejimkujik National Park, Canada (1988-1993)

Kerekes, Joseph and Duggan, Michael and Bates, Duncan and Boros, Gabe and Tordon, Robert (1997) Abundance and distribution of fish-eating birds in Kejimkujik National Park, Canada (1988-1993). MAGYAR VÍZIVAD KÖZLEMÉNYEK, 3. pp. 81-89. ISSN 1416-1389 (nyomtatott); 1419-6107 (elektronikus)

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Abstract

The inventory and baseline characterization of breeding populations of aquatic birds in 40 lakes in Kejimkujik National Park (385 km") in 1988 seems to confirm that contrary to previous assumptions these bird populations are of sufficient density to warrant their study with respect to the impact of acid precipitation The six year breeding population data obtained since 1988 confirmed that the successfiil breeding of fish-eating bird such Common Loon and the Common Merganser is controlled by the amount of fish available in a lake which is in turn controlled by the nutrient supply (phosporus) in the lake. At least 20 ha of lake surface is required in the Park to provide enough fish to support a territorial pair of loon. 40 ha or more is needed to support the breeding of either if the Common Loon or Common Merganser and 80 ha or more is necessary to support two or more either of these species or their combination The six years of breeding data shows that the number of territorial loon pairs remains stable («39 pairs) while the number of chick fledged may vary considerably from year to year (average 11 3, range 5 to 18) A large number of the non-breeding loon population spend their summer in the ocean The relative closeness to the sea coast («40 to 60 km in two directions) ensures that all the suitable loon territory in these lakes is soon filled when they become vacant. This may give an explanation of the low ratio (0.29) of loon chick/territorial pair in Kejimkujik compared to other more continental populations (>0.5) distant from the sea. Some of the year to year fluctuation of breeding success of loons max be the result of changes in water levels during the nesting period, but other unknown factors are at work as well.The total number of Common Merganser brrods is very stable from year to year (average 13.4, range 12 to 16)

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