The shore-and waterbirds on some grazed and ungrazed islands on the Finnish west coast

Abstract

The study deals with the shore- and waterbirds on 12 low moraine islands (areas 2.0-23.6 ha) on the Finnish east coast. Five of the islands were still grazed during the study year or until very recently, while the other seven were mostly covered with forest . Of the shore- and waterbirds counted, 86% nested on the grazed islands. The density of breeding birds was significantly higher on the grazed islands than on the ungrazed ones, but there was no statistically significant difference in the numbers of species or pairs. Although many topographic features of the islands may influence the composition ofthebird fauna, there was a significant correlation between theproportion ofopen areas (i .e . low grass meadows and areas with scanty bushes) and the density of the shore- and waterbirds . The bird density was 1 .5-13.3 pairs/ha on the ungrazed islands (13-26% open areas), and 10.6-74.5 pairs/ha on the grazed islands (28-100% open areas) . I suggest that continuation of grazing for keeping at least 40% of a grazed island open would be a practical and cost-effective method of ensuring a fairly rich shore- and waterbird fauna.