BREEDING BIRD COMMUNITIES AND ENVIRONMENTAL VARIABLE CORRELATES OF SCOTTISH PEATLAND WETLANDS

The majority of lochs and water courses in an area of northern Scotland were visited during July 1988. Breeding waterfowl and details of environmental variables were recorded for each site and subjected to multivariate classification techniques. Non-hierarchical classification identified seven habitat types on the basis of environmental parameters. These corresponded well with, and further sub-divided, categorisation using conventional trophic-level habitat type classifications. A hierarchical approach, using TWIN-SPAN, classified twelve waterfowl groupings based on the presence of indicator species. This approach identified characteristic community types and groupings with high diversity and hence conservation importance. Correspondence between habitat classifications and waterfowl communities was reasonable, but failure to identify key features of wetland complexity was probably the reason for the inability to identify clear relationships. Induction analysis was used to show that waterfowl species with the most restricted distributions characterised the main groupings, with Black-throated Diver and Common Scoter showing preferences for mesotrophic/eutrophic waters with islands, where peaty waters drain onto base-rich sandy substrates. Greylag Geese occurred on large acidic oligotrophic lochs and Wigeon on base-rich streams. The need for catchment-wide site-safeguard and management programmes to safeguard the wetlands of greatest significance is discussed.