Grey Heron Ardea cinerea productivity in relation to habitat features and different spatial scales

摘要

Life history traits of birds like survival or reproduction are strongly related to habitat features which affect food and nest-site availability. However, impact of habitat variables on life-history traits, which may be scale-dependent is barely studied. We investigated the relationships between landscape features and productivity (expressed as the number of 21-38 day old chicks per nest) of a colonial waterbird, the Grey Heron Ardea cinerea in northern Poland. In 2014 we analysed the landscape features (hydrographic features, habitat area, habitat patchiness and distances to the nearest water bodies, coastline, rivers/canals, buildings and roads) around the six colonies. We analysed all those features in four spatial scales around the colony: close proximity of the colony (0-1 km), closer foraging grounds (0-10 km), far foraging grounds (0-20 km) and far foraging grounds excluding close foraging areas and proximity of the colony (10-20 km). The differences in productivity among the colonies was not significant in the studied year (mean number of chicks SD: 3.57 +/- 0.52). At each spatial scale excluding 10-20 km radius, Grey Heron productivity increased with increasing habitat heterogeneity and decreased with increasing length of rivers/canals and area of pastures. The results of this study indicate that the spatial scale of 0-10 km was the best to indicate relationships between landscape features and productivity in herons. Distance to the nearest river/canal banks, buildings and roads were related positively to productivity. Our study revealed the importance of landscape complexity of aquatic and terrestrial habitats for the Grey Heron productivity.