THE EFFECT OF SUMMER COTTAGES ON LAND BIRD NUMBERS IN A FINNISH ARCHIPELAGO

The effect of summer cottages on land bird numbers was studied in the archipelago of SW-Finland. Bird fauna was very similar on cottage and non-cottage islands, with the following exceptions: The Wagtail Motaci lla alba was significantly (P < 0.05) more abundant on cottage islands . The Oystercatcher Haematopus ostralegus and the Willow Tit Parus mon tanus were nearly significantly (P < 0.10) more abundant on non cottag e islands. In the grouping of species based on nesting habits, birds n esting in nest boxes and other man-made structures were more abundant on cottage islands. The mean species richness and the Shannon-Wiener d iversity index H' were significantly greater on cottage islands than o n non-cottage islands. However, if the data are combined and treated a s one sample for cottage islands and the other for non-cottage islands , the differences in species richness and diversity between island gro ups disappear.