The seabirds of NW Aland - a basleline study 1991

The seabirds within a defined archipelago-gradient (inner, sheltered parts to open, exposed maritime zone) on NW Åland (N. Baltic Sea) was investigated from April through September 1991 in order to qualify and quantify the bird populations and the bird community (both migrating and nesting species and populations) of the area. The genreal aim was to obtain a solid basis for future monitoring of the bird communities in relation to environmental change. The investigation was conducted by counting the birds within a physical gradinet (6 zones) ranging from the innermost bays (including a lake as a reference) through the entire archipelago to the open coast from 40 points on shore within sight from each other. Thus the entire area was covered during each of the five countings (April, June, July twice, and September) conducted. 63 species were recorded, at least 23 of which breed within the area and another 13 spp probably do. The remaining 27 spp utilise the area only during the spring and fall migrations. The innermost archipelago has a waterfowl community very similar to that of the lakes on Åland. The "limnic" character gradually diminishes towards the open sea, and in the middle archipelago the "marine" components of the community begin to dominate. Many of the biotopes studied and the species utilizing these are worth conservation, and we belive that the relatively unaffected status of this archipelago gradient even from an international perspective makes this area a valuable reference area for long-term monitoring of the bird community as a means to follow man-made changes of the entire ecosystem