Effect of lake acidity and morphometry on the distribution of aquatic birds in southern Quebec

Abstract

More than half the lakes in the deciduous and boreal forest regions of southern Quebec harbour at least one aquatic bird species during the nesting period. Although the number of nesting pairs per lake is generally small, those pairs are most commonly seen on lakes with a surface area of more than 15 ha, a winter pH lower than that of normal rain (i.e. < 5.6), an irregular shore configuration marked by abundant riparian vegetation, and islands.In a correspondence analysis, the first axis, representing lake acidity, explains 68% of the total variance. The common goldeneye Bucephala clangula, which is frequently seen on the most acidic lakes, and the American black duck Anas rubripes, which tends to avoid acidic lakes, show the largest contributions to that axis. The second axis describes an altitude/surface area gradient and brings the cumulative percentage of explained total variance to 94%; the great blue heron Ardea herodias and the common loon Gavia immer primarily use large, low‐altitude lakes, whereas the ringnecked duck Aythya collaris and the American black duck are often found on the smaller, higher‐altitude lakes. Those results are discussed as they relate to the feeding requirements of the various species of bird and the biology of their main prey. The ecological segregation of the three waterfowl species is attributed to interspecific competition.