A 33-year Study of Hazel Grouse Bonasa bonasia in the Bohemian Forest, Šumava, Czech Republic: Effects of Weather on Density in Autumn
2007
Klaus, Siegfried
The only long-term census of hazel grouse Bonasa bonasia in Central Europe was conducted during 1972-2004 on a 100-km² area of the Bohemian Forest, Šumava, Czech Republic. To obtain a density index in October, I recorded indirect signs of hazel grouse, such as dust bathing sites, feathers, droppings or tracks, and reactions to a whistle that imitates the male territorial song along fixed routes covering 80 km in total. During the 33 years of counting, I found no statistically significant trend in the fluctuating numbers. I also looked for the influence of weather on hazel grouse abundance. Analysis by stepwise multiple regression suggested that six weather variables were correlated with the annual rate of change of hazel grouse density in autumn, explaining 44%% of the variation in density: mean temperature and total precipitation in April (highly significant positive correlations) and mean temperature and total precipitation in May and September (significant negative correlations). The results for April and May seem to indicate a positive effect of rainfall and temperature in April on reproductive success in the pre-laying period, but a negative effect of rainfall in May on chick survival.
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