Habitat use and diet of Common Snipe Gallinago gallinago breeding on moorland in northern England

摘要

Capsule Moorland breeding birds were associated with marshy grassland, acid flush and unimproved acid grassland, where their diet was dominated by earthworms and tipulid larvae. Aims To quantify breeding Snipe densities in upland habitats and to examine diet and the structural characteristics of feeding areas. Methods Snipe were surveyed on four areas (total 44 km super(2)) near Otterburn, Northumberland in 2000 and 2002. The use of seven habitat types was assessed from estimates of relative density from alpha generalized linear model. Five variables were measured at Snipe flushing locations and compared with measurements made at random points. Diet composition and seasonal changes were determined from faecal samples collected during April, May and June. Results Mean breeding Snipe density was 2.28 plus or minus 0.25 birds/km super(2) (approximately 1.14-1.34 pair/km super(2)). Snipe densities on marshy grassland or acid flush were 3.4-times higher than on heath and heath/grass habitats. Densities on unimproved acid grass were 2.7-times higher than on improved grassland. Within habitats, Snipe were flushed from locations that were closer to ditches or pools and characterized by wetter soil and more uneven swards than randomly selected points. Snipe diet during April-June consisted mainly of earthworms and tipulid larvae, which accounted for 61 plus or minus 7% and 24 plus or minus 6% of the dry weight of prey items ingested, respectively. A wide variety of surface-active and aquatic prey were also taken, especially in April. Conclusion Snipe breeding on moorland in upland Britain depend on unimproved marginal grassland and wet habitats, owing to the species' specialized feeding requirements.