Landscape-dependent use of a seed-rich habitat by farmland passerines: relative importance of game cover crops in a grassland versus an arable region of Scotland.

Abstract

Capsule Game cover crops in a pastoral region of southwest Scotland supported passerines at more than twice the density found in similar crops in an arable region.
Aims To investigate the use of seed-rich habitats (game cover crops) by farmland passerines in the agricultural grasslands of southwest Scotland relative to the arable east.
Methods Birds were counted in game cover crops and conventional crops on nine farms in Dumfries and Galloway, and Ayrshire, during the winters of 2003/04 and 2004/05. Similar data from eastern Scotland were re-analysed to compare the relative use of the two crop types in the contrasting regions.
Results Passerine densities in game cover crops in southwest Scotland were two orders of magnitude greater than in conventional crops. Furthermore, densities within grassland game cover crops were more than double those in arable areas and densities in grassland conventional crops were just 14% of those in equivalent arable habitats.
Conclusion The significantly greater difference between passerine densities in game cover crops and conventional crops in a grassland versus an arable region of Scotland could not be explained by differences in the bird communities, crop types, boundary habitats, weather, observer effects or survey methods used. We suggest that game cover crops may be more attractive in grassland regions because alternative food sources are rarer than in arable regions.