Abstract
We studied behaviour of large gulls recently marked with wing-tags at loafing sites at an inland refuse dump using focal birds. During the first 3-4 weeks after marking, wing-tagged gulls spent more time preening at the refuse dump than unmarked birds, which usually did not preen there, while no difference between those two groups was observed at other sites. The possible reasons for preening on the refuse dump are that marked gulls either avoided flying to the loafing water because wing-tags impaired their flight, or showed displacement behaviour.