Abstract from BTO Research Report No 275:

Henderson, I.G., Vickery, J.A. & Carter, N. (2001) (Published Aug 03)

The relative abundance of birds on farmland in relation to game-cover and winter bird crops.
ISBN 1-902576-76-4

Executive summary

1. This report describes an analysis of the densities of gamebirds and indigenous bird species recorded on “winter bird crops” (i.e. game-cover crops and wildbird mixes within the set-aside scheme and Arable Stewardship Pilot Scheme) over three winters between October 1998 and March 2001.

2. The survey comprised a total of 192 selected from English arable and mixed farming regions. On each farm, volunteers were allocated a survey plot comprising one winter bird crop (usually a strip or margin) and between two and four neighbouring conventional “crops” (including grassland). Volunteers counted the birds on their plot six times between October and March in each winter, by walking around and through (where possible) the winter bird crop and nearby fields.

3. Bird densities on winter bird crops were generally higher than on conventional crops, except for Grey Partridge, Skylark, Rook and Reed Bunting. Among winter bird crops, kale, quinoa, turnips and seeding cereals were most consistent in supporting high densities of birds, including Biodiversity Action Plan (BAP) species such as Grey Partridge, Skylark, Song Thrush, Tree Sparrow, Bullfinch, Linnet and Corn Bunting. Brassicas such as turnips, rape or mustard were also predominant crop supporting higher densities of species than sunflowers, buckwheat or phacelia for example.

4. In late winter (February/March) there was greater contrast between crops in their support of birds, but kale, cereal stubbles and maize were the main crops still supporting birds. Sunflowers were largely depleted by December.

5. Densities of birds on Arable Stewardship plots were generally lower than on conventional wildbird crops. Arable Stewardship plots tended to comprise a higher proportion of buckwheat, sunflowers and grasses and a lower proportion of kale, maize, linseed, quinoa, cereals and turnips than conventional wildbird crops.

6. Preliminary recommendations indicate that, for most species, winter bird crops are preferred to conventional crops. In particular, relatively simple crop mixes that include seeding cereals, brassicas (kale, rape, turnips and mustard), quinoa or linseed would be most effective for attracting the widest range of bird species to arable farmland. Higher densities of Grey Partridges, Tree Sparrows and Reed Buntings tended to be associated with weedy winter bird crops. Notably, as well as seed-eating species, both kale and quinoa attracted high densities of insectivorous species such as thrushes and Dunnock.

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