Michał Budka, Paweł Ręk, Tomasz S. Osiejuk, Krzysztof Jurczak
Ornis Polonica 2012, 53: 165–174
https://doi.org/10.12657/ornis.2012.3.0
Abstract: In 2007–2011, 12 localizations in Poland were controlled each once. In total, 238 surveyed 1 km² UTM grid squares fulfilled two requirements: (1) the observer could have heard each potential bird from the distance of less than 500 m, and (2) spent more than 40 minutes within square. In total, 441 calling corncrake males were recorded. Birds inhabited mainly cultivated and uncultivated meadows. Rarely, birds were observed in the fields, pastures and forest plantations. The average density of calling males varied from 1.3 to 6.6 per 1 km² of potential habitats, depending on the localization. However, local densities were considerably higher: up to 10–25 calling males per 1 km². The average distance between a territorial male and its nearest neighbour was 316 meters, but 67% of males had the nearest neighbour in the range of 50–300 meters. Within the hearing distance, which was assumed here as a 1 km, territorial male had 6 calling individuals on average. Single males were observed in less than 4% cases. Results of this study suggest that the corncrake can reach high densities in suitable habitats. There was a tendency of males to cluster in loose groups, which consisted of few to more than ten males. Such groups were observed even in large, homogenous habitats. Such behaviour of males may increase mating success and indicates irregular distribution of the females. In this study, possible interpretations of the results of the corncrake surveys, in the view of the current knowledge, are discussed.
