DENSITY-DEPENDENT HABITAT SELECTION IN NIGHTINGALE (Luscinia megarhynchos C. L. Brehm) IN SELECTED WINDBREAKS OF SW SLOVAKIA

摘要

The study is based on the theory that birds at low population density occupy the most suitable habitat, whereas with increasing the density, a part of the population occupies marginal habitats at a greater range. The population density of the nightingale {Luscinia megarhynchos) was monitored by means of the territory mapping method in windbreaks of SW Slovakia during six breeding seasons. The population of nightingale reached its maximum in 2000 (45 breeding pairs, 3.55 BP/ha) and the minimum in 1997 (31 breeding pairs, 2.44 BP/ha). Comparing the vegetation structure of nightingale territories occupied in both years (1997 and 2000) and territories occupied just in the year at the highest population density (2000), the two types of habitat selected by nightingale were distinguished by means of discriminant analysis. The habitat selected in both years was characterized by lower herb cover values, higher tree diversity values and smaller shrubs. At the high population density, a part of the population selected also the habitat with higher herb cover values, lower tree diversity values and taller shrubs. Considering the spatial structure of a windbreak network, the windbreak intersections and dead-ends were preferred by nightingale, whereas the straight windbreak sections were selected only at the high population density. To support the definition of optimal and suboptimal habitat for nightingale in windbreaks of SW Slovakia, reproductive conditions of population should be acknowledged. To determine the general habitat selection, the year-to-year fluctuations in population density should be considered, hence the short-term ecological studies give just weak implications.