Black-headed gull monitoring

The field work consisted in monitoring more than 400 ponds annually to check their status (drained or not) and detect colonies, usually by plane. When a colony was detected, the number of breeding pairs was checked on the ground by two observers.

Birds were also ringed almost every years in some colonies (most in the major colony called La Ronze) and resighting efforts were made to detect these birds almost every year in a sample of breeding colonies (again most on the major colony of La Ronze). Ringing was made by catching chicks in the colony or with canonnet in adjacent fields. Resightings were made from a floading hide.