A survey and GIS-based estimate of the breeding population of Great Snipe Gallinago media in Central Norway

摘要

Capsule By using a GIS-model to identify suitable breeding habitats for Great Snipe in Central Norway, we estimated a total of 276 leks holding approximately 2700 males. Aim To estimate the size of the Great Snipe population in central parts of the species remaining breeding areas in Western Europe. Methods GIS-analysis identified an area of 528 km(2) as suitable habitat for Great Snipe in the total study area (22 000 km(2)). Complete surveys were made in 8% of these habitats by using a subset of 53 sampling areas. Results A total of 28 Great Snipe leks were found within the sampling areas. Ten of these were found in previously known lek areas, while 18 leks were found in areas with no previous knowledge of leks. Extrapolating the lek density and the lek size found in the surveyed areas, resulted in a total estimate of 276 Great Snipe leks holding approximately 2700 lekking males. The leks were found on open fens along the forest edge and were mainly situated on base-rich bedrocks. Mean altitude of the leks was 570 m. Conclusion The total population of Great Snipe in Norway was previously assumed to comprise 5000-15 000 lekking males or 'pairs'. By extrapolating the densities of leks found in Central Norway to a national scale, we expect the true breeding population of Great Snipe to be approximately 13 500 males. Changes in the elevation of the tree limit and increased overgrowth, as a result of reduced grazing pressure and/or global warming, are possible threats that may reduce the availability of preferred Great Snipe habitats and increase population fragmentation