Ardea
Official journal of the Netherlands Ornithologists' Union

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Roedl T. (1999) Environmental factors determine numbers of overwintering European Stonechats Saxicola rubicola: A long-term study. ARDEA 87 (2): 247-259
In this study the relationship between the number of European Stonechats Saxicola rubicola at a winter site in Israel and the local rainfall, air temperature, and arthropod abundance was examined. In some years population size declined to about one third of the initial size, while in others it remained almost constant. The decline of bird numbers was mainly due to the disappearance of young, unpaired individuals. The magnitude of the decline in numbers was correlated with timing and amount of winter rainfall, which is crucial for the growth of the vegetation after a long dry summer period. Early winter rainfalls had a much stronger impact than total winter rain. The decline in numbers was also correlated with arthropod density in pitfall traps; however, it was not correlated with air temperature. The relative extend to which density-dependent and density-independent factors determine the size of the wintering population of European Stonechats is evaluated


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