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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Decline of the Black Grouse Tetrao tetrix population in east-central Poland.
Auteurs :	Zbigniew Kasprzykowski, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (123(5) 2002)
Article en page(s) :	253-258
Résumé :	The study was conducted in the Mazovian and South-Podlasian Lowlands, east-central Poland, covering ca. 13% of the area of Poland. The data for 1975-2000 are based on the author's own observations and material gathered by the regional card-index of the Mazovian Society for the Protection of Fauna. In addition, in 1989-2000 population abundance was surveyed on 8 plots. In the mid-1970s, 96 leks were known, mostly from the eastern part of the region. Over a period of 10 years (by 1985) leks disappeared from central and southern parts of the Mazovian Lowland Black Grouse abandoned over 60% of the known refuges. Early in the 1990s this process continued, and lekking grouse were recorded mainly from northern part of the region. Surveys in 1997-2000 revealed only 8 leks. This means that over a period of 25 years, the number of leks decreased by 92%. A detailed analysis of changes in numbers was possible for northern portion of the grouse population. At the end of the 1980s and early in 1990s, 13-27 individuals were observed there on 8 plots. In 1998, the number of birds varied between 1 and 6 on five plots, they were absent from the remaining three plots. A comparison of numbers for 1990 and 1998 showed a deline from 101 to 17 individuals, that is by 83%, over a period of 8 years. The number of males declined by more than 80% and that of females by about 70%. The mean annual rate of decline was 10-13%. The number of individuals per lek decreased with the total population. Early in the 1990s, groups of 8-20 (8.2 on average) lekking males were noted, whereas in 1998, only four males were present on the biggest lek, and only single birds were observed on the remaining leks (x = 1.8 male/lek). The most important factors causing this decline are assumed to be increasing predation, mainly by foxes, hunting on leks and the weather conditions in winter (thin snow cover). Co-occurrence of Pheasants and changes in the natural habitat are believed to be of less importance in the study region.

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