Ornis Hungarica. vol.8 Suppl. 1.. (1998) p.27-32.
Populációváltozási indexek a magyarországi énekesmadár fajok állományaira 1988 és 1995 között
Changes and fluctuations in the populations of the common breeding bird species are increasingly important to monitor environmental changes and formulate recommendations, and conservation. The point count of breeding passerine birds is one of the monitoring programs of the Hungarian Ornithological Society, started in the late 80-ies. The method we applied, the so-called 5-minute bird count, is the same which has been used since 1975 in Denmark and throughout Europe. Each observer selected a route with 20 fixed points. Distances between the points were 200 m in woodland and 300 m in open areas (grasslands or reedbeds). Birds were counted yearly between 1 and 20 May All birds seen or heard were noted. The total number of counts varied between 23 and 36 from 1988 to 1995. Population indices were calculated for the 20 most common species. Significant changes were found in 5 species and 8 cases. The 20 species can be grouped into 3 categories according to their population indices. The Wood Warbler showed the four largest significant changes between two consecutive years, which could be affected by the drought on its migratory route, in the Sahel region.