The Feeding Ecology and Conservation of Wigeon Wintering at the Ouse Washes, England

Abstract

Following the creation of wildfowl refuges on the Ouse Washes, mainly between 1965 and 1970, the annual winter maximum numbers of wigeon increased almost 3-fold and the usage (wigeon days) more than 5-fold. The birds arrived earlier in autumn, and in recent years peak numbers occurred before the shooting season ended. The extent of winter flooding and intensity of shooting previously affected the usage of the area, and the birds have now been made partially independent of these. The feeding ecology was studied in 1968-1972. Wigeon are chiefly diurnal feeders on the Washes, and in Jan. and Feb. they spent 91% of the daylight hours feeding (9.6 of 10.5 h). Feeding activity is high immediately after dawn, decreases slightly in mid-day and increases again towards dusk. A similar pattern was noted when birds fell on winter-sown wheat outside the Washes, but when they fed in autumn on stubble grain they did so in 2 periods, one after dawn and the other before dusk. Grazing was the most common feeding method but at high water levels upending was also frequent. During deep flooding, wigeon fed in association with Bewick''s swans and diving coot. More than 80% of the diet consisted of grass leaves, and 3 spp. of fine grasses [Dactylis glomerata, Holcus lanatus and Agropyron repens] made up nearly 3/4 of this. Animal material was taken rarely and usually incidently to vegetation or seeds. Only 1 of 235 ducks had fed actively on chironomid larvae. Only 12 of the ducks examined contained foods from surrounding agricultural fenland, but this underestimated their use of arable land, since most of it occurs outside the shooting season, when few specimens were available. Stubble grain is taken in autumn, and sprouting winter wheat is grazed in winter and spring. The carrying capacity of the refuge areas for wigeon can be increased still further by improvements in the management of water levels and summer grazing. The use of non-refuge areas could be doubled if shooting ceased. Wigeon are resorting increasingly to inland habitats which are now more important than the traditional coastal mudflats and saltmarshes. This may lead to increasing conflict with farmers as the birds resort to arable land. Inland waters are likely to freeze in hard winters, and displaced birds could be in difficulty as the alteration of estuarine habitats continues.