Maize stubble as foraging habitat for wintering geese and swans in northern Europe

Agricultural crops have become increasingly important foraging habitats to geese and swans in northern Europe, and a recent climate-driven expansion in the area of maize fields has led to a rapid increase in the exploitation of this habitat. However, due to the novelty of maize foraging in this region, little is known about the abundance and energetic value of this resource to foraging birds. In this study we quantify food availability, intake rates and energetic profitability of the maize stubble habitat, and describe the value of this increasingly cultivated crop to wintering geese and swans in the region. Our results indicate that the maize resource varies considerably among fields and years, but also that the energetic returns from maize foraging is substantial. As such, fields with extensive spill allow foraging birds to fulfill their daily energetic demands in 4 h of active foraging. Both the area of cultivated maize fields and the importance of this habitat to foraging birds are expected to increase in years to come. This may alleviate conflicts with other more vulnerable crops such as winter cereals, and have the potential to affect migratory decisions, site use and population dynamics of geese and swans wintering in northern Europe.