The effects of improvement of upland, marginal grasslands on the distribution and density of breeding wading birds (Charadriiformes) in northern England.
Agricultural improvement of grasslands, at the upper altitudinal limit of agricultural practice, subsequently referred to as the uplands, has progressed rapidly in recent years. The impact on breeding wading birds (Charadriiformes) was assessed in the years 1985–1987 by comparing the densities and species of waders using improved and unimproved grasslands in northern England. Improvement (drainage, inorganic fertilizing and, in some cases, reseeding) resulted in the virtual disappearance of snipe Gallinago gallinago and marked reductions in the density of, and in the proportion of fields used by, redshank Tringa totanus, curlewNumenius arquata and lapwing Vanellus vanellus. In contrast, oystercatchers Haematopus ostralegus have started to nest on improved grasslands in areas where they have not previously bred. Thus the species composition on unimproved grasslands have changed following improvement. It is evident that within large areas containing many fields, the overall density of waders has declined as the percentage of fields that have been improved in the post-war period increased. This suggests waders have not simply redistributed themselves between improved and unimproved fields but rather that there has been a marked, overall decline in the numbers of waders in areas where improvement has taken place.