The effect of the spatial distribution of winter seed food resources on their use by farmland birds.

Published online
11 Oct 2006
Content type
Journal article
Journal title
Journal of Applied Ecology

Siriwardena, G. M. & Calbrade, N. A. & Vickery, J. A. & Sutherland, W. J.
Contact email(s)

Publication language
UK & England


Agri-environment measures providing winter seed are central to current management activities aiming to reverse granivorous farmland bird declines. Previous research has considered the effectiveness of particular agri-environment options, but the influence of their distribution in the landscape, an important factor in determining cost-effectiveness, has received less attention. We used a large-scale field experiment in eastern England, conducted during 2002-03 and 2003-04, featuring 10 replicates of a spatial arrangement of 7 artificial feeding stations separated by different distances, to investigate bird movements between discrete winter food resources. Feeding sites were established and bird use monitored at least weekly over two winters (November-March). Habitat type in areas surrounding the feeding sites was also recorded. Two measures of feeding site use were analysed as functions of the distance from the nearest alternative feeding site, controlling for ambient resource availability, for 11 passerines (chaffinch, Fringilla coelebs; reed bunting, Emberiza schoeniclus; yellowhammer, Emberiza citrinella; robin, Erithacus rubecula; dunnock, Prunella modularis; great tit, Parus major; house sparrow, Passer domesticus; goldfinch, Carduelis cannabina; greenfinch, Carduelis cannabina; black bird, Turdus merula; and blue tit Parus caeruleus). Feeding site use varied significantly with separation distance for the 9 species. For most, both maximum counts and bird minutes were higher at more isolated sites, but the opposite was true for yellowhammer and reed bunting. Most relationships incorporated significant thresholds at separations of around 500 m, with low site use below the threshold and high above it (or vice versa). The results suggested that species such as chaffinch and blue tit made disproportionately more use of food at isolated sites than at clumped ones, but that reed buntings and yellowhammers used food in proportion to its availability, moving freely between more clumped patches. In both cases, birds tended to share resources separated by 500 m or less. At greater separations, resources tended to be used by discrete groups of birds. Radio-tracking and colour-ringing work produced corroborative evidence. The response of birds to the experimental food resource distribution implies that creating resource patches more than 1.0 km apart should be most cost-effective, a recommendation that can inform agri-environment scheme planning directly. However, this distance may represent a minimum because birds might locate standing crops more readily than inconspicuous artificial food patches.

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