The effect of night grazing by wigeon ( Anas penelope) on winter-sown wheat in Japan and the efficacy of black plastic flags as scaring devices

Abstract

From November 1994 to April 1995 a flock of up to 247 wigeon ( Anas penelope) roosted on an artificial pond during the day at Misato City, Japan. At night some or all of this flock fed on nearby winter-sown wheat ( Triticum aestivum L.). We conducted an experiment to test the effectiveness of black plastic flags as scaring devices. Flags were deployed at 50 flags ha −1 in five wheat fields which were each paired with an adjacent unprotected field. Grazing intensity on the flagged fields was reduced significantly as measured by dropping density. Only 7.7|X% of all droppings counted were found in the flagged fields. The wigeon did not habituate to the scaring devices during the experiment. In an unprotected field, loss of yield was estimated at 83% by comparing differences inside and outside exclosures. In an adjacent protected field with exclosures there was no statistically significant loss.