Action: Create uncultivated margins around intensive arable or pasture fields for birds
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- A replicated, controlled study from the USA found that three sparrow species found on uncultivated margins were not found on mown field edges. A replicated study from Canada found fewer species in uncultivated margins than in hedges or in trees planted as windbreaks.
- Three replicated studies from the USA and UK, one controlled, found that some birds were associated with uncultivated margins, or that birds were more abundant on margins than on other habitats. One study found that these effects were very weak. Four replicated studies (two of the same experiment) from the UK, two controlled, found that uncultivated margins contained similar numbers of birds in winter, or that several species studied did not show associations with margins.
- A replicated, controlled study from the UK found that yellowhammers Emberiza citrinella used uncultivated margins more than crops in early summer, but use fell in uncut margins in late summer. Cut margins however, were used more than other habitat types late in summer.
- A replicated study from the UK found high rates of survival for grey partridge Perdix perdix released in margins.
This intervention allows vegetation in field margins to regenerate naturally, without planting, although it can involve subsequent mowing. The margins are not fertilised and only spot-treated with herbicides if necessary.
Supporting evidence from individual studies
A replicated, controlled study in February 1997 and 1998 on eight arable farms in North Carolina, USA (Marcus et al. 2000), found that sparrow species were significantly more abundant on farms with uncultivated field margins (set up in 1996) than on those with mown field edges (34-36 sparrows/ha for uncultivated margins vs. 6-21 sparrows/ha for mowed edges). In addition, uncultivated field margins contained three species (white-throated sparrow Zonotrichia albicollis, field sparrow Spizella pusilla and chipping sparrow S. passerina) not found in mowed edges; all four species found in mowed edges (savannah sparrow Passerculus sandwichensis, song sparrow Melospiza melodia, swamp sparrow M. georgiana and dark-eyed junco Junco hyemalis) were also found in uncultivated field margins. In total, 93% of birds detected in field edges were sparrows.
A replicated study in southern Quebec, Canada, in July 1995 (Jobin et al. 2001), found that herbaceous borders around arable fields held significantly fewer individuals and species than either hedges or trees planted as windbreaks (19 species found in 17 herbaceous borders, at 19 birds/ha vs. 25 species at 51 birds/ha for 17 windbreaks and 39 species at 57 birds/ha for 27 hedges). Differences were significant, even when adjusting for different sample sizes.
A replicated study in 1999 and 2003 on 256 arable and pastoral fields across 84 farms in East Anglia and the West Midlands, England (Stevens & Bradbury 2006), found that a combination of creating planted (see ‘Plant grass buffer strips/margins around arable or pasture fields’) and uncultivated margins around fields was strongly positively associated with four out of twelve farmland bird species analysed. These were skylark Alauda arvensis (a field-nesting species) and chaffinche Fringilla coelebs, whitethroat Sylvia communis and yellowhammers Emberiza citrinella (all boundary-nesting species). The study did not distinguish between uncultivated and planted margins. This study describes several other interventions, discussed in the relevant sections.
A replicated controlled trial on one farm in Warwickshire, UK in 2005-2006 (Pywell & Noweakowski 2007) found that field corners or margins left to naturally regenerate for one year did not have more birds in winter (species or individuals) than control crop plots. Average counts were one bird/plot or fewer for both treatments. The plots were left as unmanaged wheat stubble for all of 2006. The crop, oats, was sown in October 2005. Each treatment was tested in one section of margin and one corner in each of four fields. Farmland birds were counted on each plot on seven counts between December 2006 and March 2007.
The second monitoring year of the same study as Pywell & Noweakowski (2007), from 2005-2007 (Pywell & Noweakowski 2008) found that naturally regenerated plots did not have more birds in winter than control cereal plots. There were two birds/plot or fewer, and 0.4-1.6 bird species/plot on average on all treatments except wild bird seed mix (see ‘Plant wild bird seed or cover mixture’). Farmland birds were counted on each plot on four counts between December 2007 and March 2008. The crop control in the second year was winter wheat.
A replicated, controlled study in May-August 2005-6 on five farms in Aberdeenshire, Scotland (Douglas et al. 2009), found that a larger proportion of early-summer yellowhammer Emberiza citrinella foraging flights were in field margins (32% of 233 flights from ten nests), compared to cereal crops (8%). However, in late summer, cereal fields were used more (up to 56% of 506 flights) and field margins less (down to 15%). In 2006, sections of margins around some nests were cut down to the soil. These patches comprised 2.3-2.4% of margin area, and were used for 2.9% of 172 foraging flights in early summer and 34% of 77 foraging flights in late summer. The authors suggest that yellowhammers used cut patches disproportionately as the uncut sections grew taller and so reduced the access to invertebrates.
A large 2010 site comparison study of 2,046 1 km² plots of lowland farmland in England (Davey et al. 2010) found that three years after the 2005 introduction of the Countryside Stewardship Scheme and Entry Level Stewardship schemes, there was no consistent association between the provision of uncultivated field margins on arable or pastoral farmland and farmland bird numbers. Although plots with field margins did see more positive population changes (increases or smaller decreases relative to other plots) of rook Corvus frugilegus, starling Sturnus vulgaris and woodpigeon Columba palumbus, the effect was small, with starlings, for example, showing increases of only 0.0002 individuals for every 0.001 km² of margin in mixed farmland plots. Other species expected to benefit from margin provision including corn bunting Emberiza calandra, grey partridge Perdix perdix, kestrel Falco tinnunculus, jackdaw Corvus monedula, reed bunting Emberiza schoeniclus, and common whitethroat Sylvia communis all showed no effect of margin management. Yellowhammer Emberiza citrinella, also expected to benefit from margin creation, showed a positive association in mixed landscapes and a negative association on grassland plots. The 2,046 1 km² lowland plots were surveyed in both 2005 and 2008 and classified as arable, pastoral or mixed farmland. Eighty-four percent of plots included some area managed according to the Entry Level Stewardship or the Countryside Stewardship Scheme. In both survey years, two surveys were conducted along a 2 km pre-selected transect route through each 1 km² plot.
A replicated study on four farms in Gloucestershire and Oxfordshire, England, in 2007 (Rantanen et al. 2010) found that grey partridge Perdix perdix released in pairs in the spring used field margins more frequently than birds released as family groups in the autumn. This study is discussed in detail in ‘Captive breeding, rearing and releases (ex situ conservation)’.
- Marcus J.F., Palmer W.E. & Bromley P.T. (2000) The effects of farm field borders on overwintering sparrow densities. Wilson Bulletin, 112, 517-523
- Jobin B., Choiniere L. & Belanger L. (2001) Bird use of three types of field margins in relation to intensive agriculture in Quebec, Canada. Agriculture, Ecosystems & Environment, 84, 131-143
- Stevens D.K. & Bradbury R.B. (2006) Effects of the Arable Stewardship Pilot Scheme on breeding birds at field and farm-scales. Agriculture, Ecosystems & Environment, 112, 283-290
- Pywell R. & Nowakowski M. (2007) Farming for Wildlife Project: Annual Report 2006/7. NERC report.
- Pywell R. & Nowakowski M. (2008) Farming for Wildlife Project: Annual Report 2007/8. NERC report.
- Douglas D.J.T., Vickery J.A. & Benton T.G. (2009) Improving the value of field margins as foraging habitat for farmland birds. Journal of Applied Ecology, 46, 353-362
- Davey C.M., Vickery J.A., Boatman N.D., Chamberlain D.E., Parry H.R. & Siriwardena G.M. (2010) Assessing the impact of Entry Level Stewardship on lowland farmland birds in England. Ibis, 152, 459-474
- Rantanen E.M., Buner F., Riordan P., Sotherton N. & Macdonald D.W. (2010) Habitat preferences and survival in wildlife reintroductions: an ecological trap in reintroduced grey partridges. Journal of Applied Ecology, 47, 1357-1364