Effects of Area and Habitat Diversity on Bird Species Richness in Lakes

Abstract

The number of presumably breeding bird species was determined for 31 lakes around Stockholm, Sweden. Species richness (S) was strongly correlated with lake size (A) but only weakly so with habitat diversity. Using stepwise regression it was found that 54-56% of the variation in bird species richness could be explained by size of area alone, and this percentage could be increased to 61-66% by adding a second variable describing habitat diversity. The effect of area as described by the equation (S+I)=CA3 yielded a z value of approximately .34, which is within the range of values observed for land and freshwater birds on oceanic islands, but considerably higher than values for land birds on continents.