Population trends of common birds in Estonia in 1983–2010

Abstract

The paper presents the set-up and development of a common bird monitoring scheme in Estonia in 1983-2010. The point-count survey of widespread terrestrial bird species was undertaken to measure long-term population changes and to produce indicators of the condition of habitat types and the wider environment. The scheme has been mostly run by skilled volunteers of the Estonian Ornithological Society. The method applied is point counting on free- choice routes and without limiting recording distance. In the Estonian scheme, each count route consists of 20 points, with 5-minute stops at least 200 m apart. In total, 143 point count routes have been in use by 89 active birdwatchers and professional ornithologists in the course of 28 years. Yearly abundance indices for 87 bird species were calculated using TRIM software. The most evident changes in bird numbers were the declines detected in 1992-1996 among farmland species, and in 2007-2010 among farmland and woodland species. The long-term population trends (1975-2010) in four countries around the Baltic Sea depend on the migratory strategy of bird species. Among trans-Saharan migrants the proportion of declining species was much higher in comparison with short-distance migrants and sedentary species. A marked difference between these countries was found among sedentary bird species - with up to 2/3 of species with increasing trends in Finland and less than 1/3 in Denmark, Sweden, and Estonia. There is a growing interest in using the results of the scheme both at the national and the international scale (PECBMS).