The effects of leg-loop harnesses and geolocators on the diurnal activity patterns of Green Sandpipers Tringa ochropus in winter

We have measured the activity patterns of wintering Green Sandpipers before and after they were fitted with geolocators attached using leg loop harnesses and compared these with a control group of untagged birds. The geolocators and harnesses represented 1.4–1.6% of the body mass of the birds. Although the proportion of time the birds spent feeding increased over the course of the winter, we found no significant effect of tagging. Tagged birds spent significantly more time preening than untagged birds (6.3% overall compared with 4.6% for untagged birds) but the effect decreased with days after tagging. There was no evidence that this small increase in preening activity led to lower survival of the birds or changes in their migration timetable.