Water bird guilds and their feeding connections in the Bodrogzug, Hungary

Abstract

Species composition, number, species diversity, and evenness of nesting bird communities were surveyed in 2001 and 2002 in north-east Hungary. The survey was aimed at foraging birds. A higher number of species and species diversity was observed in the oxbows compared to that of the eupotamon-type areas, and was correlated with the more luxuriant vegetation covering the water surface. The species evenness value of the oxbows was lower than that of the flowing river. The number of species and species diversity in riparian areas covered with trees were higher than those in areas covered only by bushes. There was a negative correlation between evenness and the diversity of species for habitats covered with water, and habitats covered with trees and bushes along the banks. The following highly protected bird species nested in the study areas: black stork (Ciconia nigra), lesser spotted eagle (Aquila pomarina), saker falcon (Falco cherrug), red-footed falcon (Falco vespertinus), and corncrake (Crex crex). Compared to the total bird fauna of the investigated area, the highest ratio of aquatic bird species was present in the oxbow areas covered with aquatic vegetation. Considering the role of aquatic birds in material and energy cycles, three main species groups were distinguished: the material-transporting group (highest number of specimens); the bioturbing group (lowest number of specimens); and the decomposition-accelerating group (intermediate numbers).