Effects of winter and early spring grazing by Wigeon Anas penelope on their food supply

Wigeon Anas penelope selectively grazed small patches of grassland near wat er. Their grazing activity affected the vegetation on which they fed, resul ting in a 52% increase in leaf production over the winter and, at the end o f winter, 4.75% higher protein levels compared with plants which were ungra zed. These responses of the plants were caused by defoliation, which stimul ated growth, and not a fertiliser effect from the birds' droppings. We sugg est that repeated feeding on the same areas is a deliberate strategy used b y Wigeon which causes an improvement in their dietary quality in late winte r and early spring.