Assessment of habitat-specific food availability using human imprinted Grey Partridge (Perdix perdix) chicks

Abstract

There is an increasing awareness of the need to evaluate agricultural practices and the effectiveness of environmental conservation measures in order to halt the overall decline in farmland birds. One major reason for Grey Partridge population collapse in Europe is the decreased chick survival rate which directly reflects the abundance and biomass of invertebrates as essential chick food. We evaluated a new methodological design using human imprinted Grey Partridge chicks as a biological assay to compare relative food availability (g / chick / 30 min) in five different habitat types in an arable landscape. On average , partridge chicks slightly lost weight during the trials in all considered arable habitat types, indicating a low invertebrate biomass but also indicating methodological limitations of our approach. The greatest weight loss was found in the conventional crops maize and wheat and on eutrophic grass tracks; the lowest in segetal vegetation patches within wheat fields and in wildflower crop cultivated as ecologically sound cosubstrate for bio-gas production. An increased defaecation rate due to the handling procedure is suggested to account for the weight loss so that invertebrate availability is discussed comparing the extent to which chicks could compensate this weight loss through food intake. Considering the discussed methodological restrictions in future studies, weight changes in human-imprinted Grey Partridge chicks provide a biologically relevant index of food availability and foraging value of farmland habitats and crops. Thus, these are suitable for evaluating and monitoring the quality of farmland habitats for the Grey Partridge.