 The reservoirs are major wintering grounds for wildfowl, including nationally important populations of shovelers and great crested grebes.They also attract significant numbers of goldeneye ducks, tufted ducks and goosanders.The reservoirs are also one of the capital's main roosting site for gulls; 70,000 of these have been recorded at one time, the majority being black-headed gulls, common gulls, lesser black-backed gulls and herring gulls.