Habitat preferences and similarities of Grey Partridges and Common Pheasants in agricultural landscapes under organic and conventional farming

Abstract

Agricultural landscapes had been inhabited by a vast number of bird species in the past; however, especially in the last decades, agricultural intensification had negatively affected habitat composition. Habitat heterogeneity decreased and the number of many species inhabiting farmland has severely declined. These landscapes still offer a home for species, but with decreasing environmental variability, less suitable habitat might be available and interspecific competition might have been altered. Agricultural fields under organic farming are often assumed to provide adequate habitats for farmland birds, thus competition for these areas might be high and affect species’ habitat selection. We compared habitat selection of two typical farmland bird species, Grey Partridges (Perdix perdix) and Common Pheasants (Phasianus colchicus), to determine the extent of habitat overlap in agricultural landscapes under organic and conventional farming in spring. Our study showed that both species preferred study squares with high habitat heterogeneity. In addition, squares with agricultural fields (e.g. without culture, winter cereals and fallow land) under organic farming were preferred by Grey Partridges, while Common Pheasants were mainly found on study squares containing agricultural fields under conventional farming. A broad habitat width in respect to food selection might have driven habitat choice of Common Pheasants; however, occupation of agricultural fields under organic farming by Grey Partridge males might also explain habitat selection of Common Pheasants. Awareness should be raised when releasing captive-rearing pheasants because interspecific competition between Grey Partridges and Common Pheasants could also affect fecundity and survival of both species.