FOOD-SUPPLY AND THE EFFECTS OF RECREATIONAL DISTURBANCE ON THE ABUNDANCE AND DISTRIBUTION OF WINTERING POCHARD ON A GRAVEL-PIT COMPLEX IN SOUTHERN BRITAIN

The Cotswold Water Park, an area of over 100 flooded gravel pits in south central Britain, supports Nationally Important numbers of wintering Pochard Aythya ferina associated with abundant Stoneworts Chara spp. Based on extensive presence/absence data and intensive biomass sampling, the submerged macrophyte communities were surveyed. Charophytes were most frequent and developed highest biomass at water depths below 3 m. Counts of wintering Pochard showed that water-based recreational activity displaced birds from lakes. Analysis of bird density showed significantly higher use of reserves with restricted bankside access than lakes where angling, walking or other bank-side activities were permitted. These in tum supported higher Pochard densities than lakes with water-based recreation.