Counting birds on farmland habitats in winter: Capsule Perimeter counts underestimate the number of birds using agricultural fields.

摘要: Capsule Perimeter counts underestimate the number of birds using agricultural fields. Aims To determine degree to which farmland may be undercounted on field surveys and factors influencing this. Methods In a study 96 fields, in were counted during walk perimeter. Afterwards transects walked across missed. Additionally national survey we looked at seen expressed as proportion total transect perimeter counts. Results obtain an accurate count requires use whole-area search methodology especially for species such Grey Partridge Perdix perdix, Snipe Gallinago gallinago, Skylark Alauda arvensis Meadow Pipit Anthus pratensis. However, large species, including thrushes, flocking finches buntings, over 90% individuals can recorded much less time-consuming method. Conclusions are likely reliable most but special efforts required few cryptic