Population changes for waterways birds, 1974–78

THE WATERWAYS BIRD SURVEY STARTED as a national scheme in the 1974 breeding season, following pilot studies by the Sheffield Bird Study Group in 1973, and has developed into one of the major surveillance projects of the British Trust for Ornithology.Rivers and canals form a most important component of the countryside for breeding birds.The waterways themselves are used extensively by specialised species such as Kingfisher and Dipper, while the bordering rank vegetation often supports species like Reed and Sedge Warblers which may not find breeding habitat on the surrounding land.Undrained wetlands or floodplains adjoining waterways often hold several species of duck and wader as breeding birds.(Scientific names of birds mentioned will be found in Tables IV andV.)However, the ecological balance of waterways is constantly under threat from human activities.The dredging, deepening and straightening often performed by river authorities in the interests of improved drainage usually requires the removal of all vegetation along one or both banks to permit drag-line access.Meanders are destroyed and the banks bevelled so that cliffs and overhangs are obliterated.Other threats to the wildlife of waterways include a major one from pollution.There is increasing use of algicides and aquatic herbicides to clear streams, drainage channels and canals, particularly in lowland Britain, and run-off of agricultural chemicals may also be a problem in some areas.Waterways which form part of nature reserves or SSSIs are not necessarily exempt.The risk of pollution is least in areas of strong angling interest, but here piscicides are used occasionally on some stretches to weed out coarse fish.Smith (1975) has detailed the methods of river management in lowland Britain and the likely effects on riparian birds, highlighting the paucity of available data from which to give advice to conservationists.The Waterways Bird Survey is designed to provide such data by quantifying the breeding avifauna on a large sample of plots throughout Britain, including plots subject to various types of management or pollution.The main aims of this survey can be summarised as, firstly, the maintenance of national population indices for riparian species and, secondly, the gathering of information on regional distribution, habitat preferences and requirements of individual species.The functions of the W.B.S. are thus similar to those performed on farmland since 1962 and in woodland since 1974 by the Common Birds Census.This is the first full account of W.B.S. data and gives details of the annual comparisons of population levels of riparian birds for the years 1974-75,