USE OF A NEW STANDARDIZED HABITAT SURVEY FOR ASSESSING THE HABITAT PREFERENCES AND DISTRIBUTION OF UPLAND RIVER BIRDS

Assessments of the habitat requirements of river birds are central to understanding their distribution and abundance. Here, we make an initi al appraisal of the suitability for this purpose of a new standardized method of river habitat survey (RHS) developed by the Environment Age ncy (EA). We carried out RHS and recorded the presence of five common birds along 74 upland Welsh streams. RHS provided significant and mean ingful correlates with bird distribution: Dippers Cinclus cinclus and Grey Wagtails Motacilla cinerea showed a significant preference for si tes with tree-related features, while Common Sandpiper Actitis hypoleu cos preferred streams with few trees but with more rough pasture and r iparian wetlands. Dippers also showed a significant preference for str eams with bridges and walls, often used as nesting or roosting sites. Mallards Anas platyrhynchos and Goosanders Mergus merganser both prefe rred sites with smoother flows, finer substrates and more emergent veg etation. For all species, multiple discriminant analysis (MDA) on RHS data predicted presence with a success rate of 50-81%. The distributio n of Grey Wagtails and Dippers was best predicted by RHS variables fro m the channel, flow, bank and riparian zone; Common Sandpiper and Goos ander distribution teas predicted best by channel and flow characters, and that of Mallard by channel features alone. In three species (Dipp er Goosander and Mallard) stream chemistry (pH) improved predictive ab ility. We conclude that RHS, although designed initially for move gene ral purposes, is a potentially important tool for describing and predi cting river bird distribution. Future developments should include asse ssments of which RHS data best predict bird distribution across a wide r army of river types and species. Incorporating other important influ ences on distribution, such as water chemistry, should both enhance pr edictive ability and allow further development to the role of river bi rds as ecological indicators.