We collected a total of 296 pellets of Eastern Marsh Harriers Circus spilonotus from their winter roosts (two sites) in Watarase Marsh, Tochigi Prefecture between January 2002 and late February 2004. Out of these pellets 18 contained a total of 24 pieces of lead shot. Although most of the pellets (14) contained only one piece of shot, two pellets included two and three pieces of shot. Among the prey species found in the pellets along with lead shot, ducks accounted for 55.6%, and doves and crows 11.1%. A significantly higher frequency of lead shot in Marsh Harriers pellets was found in January and February, during the open season for game birds. Although lead poisoning is not yet known to have had any profound effect on the harriers using the study site, care must be taken to protect them from lead poisoning.