Comparative diurnal and nocturnal diet and foraging in Eurasian Golden Plovers Pluvialis apricaria and Northern Lapwings Vanellus vanellus wintering on arable farmland

Knowledge of diet and intake rates are useful first steps in understanding the distribution and behaviour of foragers. The diet of Golden Plovers and Lapwings feeding on arable farmland has been rarely studied, yet these species increasingly occupy this habitat in winter. They are known to feed at night but little is known about their diet and foraging success at night. This study aimed to describe and compare diurnal and nocturnal foraging behaviour in order to explain spatial and temporal patterns in foraging. Over three winters (1999/2000-2001/02) diurnal and nocturnal observations of focal individuals and collection of faecal samples were used to reconstruct diet and quantify intake rates across a range of arable habitats. Numerically, arthropods (mostly Carabids and millipedes) were the main diurnal prey types but by biomass, small earthworms were the major prey items. Diurnal intake rates were low but comparable with other studies of these species, prompting questions concerning the profitability of feeding on agricultural farmland and the pause-travel foraging mode. Nocturnal intake rates were up to 50% higher due to a greater reliance on catching large earthworms at night. Diurnal intake rates were highest during mild weather and on grass and sugar beet stubble fields; they were lowest on cereal crops, yet this was the habitat most consistently occupied. Current methods for assessing earthworm abundance limit further explanation of foraging behaviour.