Nocturnal and diurnal activity patterns and roosting sites of green sandpipers Tringa ochropus wintering in southern England

Abstract

A radio telemetric study of Green Sandpipers at their wintering site, a disused watercress bed in southern England, shows that they alternate between the watercress bed and a nearby gravel pit complex over the course of the autumn and winter. Birds spent most days feeding at the watercress bed and roosted overnight in the gravel pit complex. During extremely cold weather in January and February the birds switched to roosting at the watercress beds. Automatic activity monitoring showed that the birds were active for around 80% of each day at all times of year. Their time active at night varied from around 16% in autumn to over 40% in cold conditions in midwinter. The hours the birds were active during the day and night in mid-winter were inversely proportional to the maximum daily temperature. The evidence suggests that a low level of night time activity is normal in Green Sandpipers but the high levels found during extremely cold winter conditions are the result of birds attempting to increase their daily food intake thus supporting the ‘supplementary’ hypothesis for nocturnal foraging. © 1999 British Trust for Ornithology.