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 so uth central Britain, supports Nationally Important numbers of winterin g Pochard Aythya ferina associated with abundant Stoneworts Chara spp. Based on extensive presence/absence data and intensive biomass sampli ng, the submerged macrophyte communities were surveyed. Charophytes we re most frequent and developed highest biomass at water depths below 3 m. Counts of wintering Pochard showed that water-based recreational a ctivity displaced birds from lakes. Analysis of bird density showed si gnificantly higher use of reserves with restricted bankside access tha n lakes where angling, walking or other bank-side activities were perm itted. These in tum supported higher Pochard densities than lakes with water-based recreation.