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Providing evidence to improve practice

Action: Undersow spring cereals, with clover for example Bird Conservation

Key messages

Read our guidance on Key messages before continuing

  • Three studies from the UK, two replicated, found that there were higher densities of some study species on undersown fields or margins, compared with other fields, or that use of fields increased after they were undersown. One of these (reported in two places) found that not all species nested at higher densities. One replicated study from the UK found that various measures of grey partridge population health declined as the amount of undersown cereal on sites increased.
  • A replicated study from the UK found no relationship between the amount of undersown cereals on a site and the productivity of grey partridge on that site.


Supporting evidence from individual studies


A before-and-after study in Dumfries, southern Scotland (Owen 1977), found that the number of barnacle geese Branta leucopsis on a mixed agricultural site and nature reserve increased from 3,200 in 1970 to 6,000 in 1975 after all cereals sown on the site were undersown from 1970 onwards. The nature reserve consisted of 220 ha of salt pasture, whilst the agricultural land was 50 ha of arable fields. Most of the extra geese fed on the arable land. In addition to undersowing, the proportion of cereals grown on the arable land decreased (see ‘Increase crop diversity’ for details) and no stock were allowed to graze on the arable land after November. The paper also discussed the impact of reducing grazing intensity, see ‘Reduce grazing intensity on permanent grassland’.



A replicated, controlled study in summer 1995 on 89 fields in the South Downs, southern England (Wakeham-Dawson et al. 1998), found that the density of singing Eurasian skylarks Alauda arvensis was higher on undersown spring barley fields than on any other field type (approximately 22 birds/km2 on four spring barley fields vs. 2-15 birds/km2 on 85 other fields). Other field types were arable fields reverted to species-rich grassland (see ‘Habitat restoration and creation: Grasslands’) or permanent grassland (‘Revert arable land to permanent grassland’); downland turf (close-cropped, nutrient-poor grassland); permanent grasslands; winter wheat, barley and oil seed rape and set-aside (‘Provide or maintain set aide areas in farmland’).



A randomised, replicated, controlled trial on four farms in southwest England, in 2003-2006 (Defra 2007), found that 12, 50 ´ 10 m plots of undersown spring barley attracted more small passerines (dunnock Prunella modularis, wren Troglodytes troglodytes, European robin Erithacus rubecula, seed-eating finches and buntings) than 12 control (not-undersown) plots. In addition, dunnocks, but not chaffinches or blackbirds, nested in hedgerows next to the sown plots more than expected, with 2.5  nests/km, compared to less than 0.5 nests/km in hedges next to experimental grass plots. Experimental plots were sown with spring barley Hordeum vulgare and a grass and legume mix, whereas control plots were managed as silage - cut twice in May and July, and grazed in autumn/winter. This study is also discussed in ‘Reduce management intensity on permanent grassland’, ‘Reduce pesticide or herbicide use generally’, ‘Raise mowing height on grasslands’, ‘Reduce grazing intensity on permanent grasslands’ and ‘Plant wild bird seed or cover mixture’ .



A replicated site comparison study on 1,031 agricultural sites across England in 2004-8 (Ewald et al. 2010) found that various measures of grey partridge Perdix perdix population health declined as the amount of undersown cereal on sites increased. There were significant changes for year-on-year density changes in 2006-2007. When undersown cereals were combined with overwinter stubbles, overwinter survival rates were lower in sites with higher amounts of undersown cereals. There were no changes in brood size or the ratio of young to old birds.



A replicated study from April-July in 2006 on four livestock farms (3 replicates/farm) in southwest England (Holt et al. 2010) - the same study as Defra (2007) - found that dunnock Prunella modularis, but not Eurasian blackbird Turdus merula or chaffinch Fringella coelebs, nested at higher densities in hedges alongside field margins sown with either wild bird seed crops or barley undersown with grass and clover, compared to those next to grassy field edges under various management options (dunnocks: approximately 2.5 nests/km for seed crops vs. 0.3/km for grass margins; blackbirds: 1.0 vs. 1.3; chaffinch: 1.5 vs. 1.4). Margins were 10 m wide, 50 m long and located adjacent to existing hedgerows. Seed crop margins were sown with barley (undersown with grass/legumes) or a kale/quinoa mix. There were 12 replicates of each treatment.


Referenced papers

Please cite as:

Williams, D.R., Child, M.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.K.H.J. & Sutherland, W.J. (2019) Bird Conservation. Pages 141-290 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.