Action: Leave uncut rye grass in silage fields for birds
- Two reviews from the UK found that leaving rye grass uncut, or with only a single cut, benefited seed-eating birds and two replicated, controlled studies from the UK found that seed-eating birds were more abundant on uncut plots.
- Two replicated and controlled studies and a review, all from the UK, found that seed-eating birds were more abundant on uncut and ungrazed plots than on uncut and grazed plots.
- A replicated, controlled study from the UK found that the responses of non-seed-eating birds were less certain than seed-eaters, with some species avoiding uncut rye grass.
In the UK, seed-eating songbirds have declined across farmland, probably in part because of a lack of winter food. Rye grass Lolium perenne seeds are a potential food source, but cutting rye grass fields multiple times a year for silage removes seed heads before they can ripen and so reduces the food available to birds the following winter. Leaving fields or plots uncut may therefore provide valuable overwinter food.
Supporting evidence from individual studies
A review of experiments on the effects of agri-environment measures on livestock farms in the UK (Buckingham et al. 2004) found that leaving rye grass silage uncut was shown to benefit seed-eating birds in winter in one experiment. No reference was given in the review for these results. The birds were only found in any numbers on plots left unmown, and were more abundant on plots left ungrazed rather than being grazed from September. Yellowhammers Emberiza citrinella and reed buntings Emberiza schoeniclus reached densities of 132 and 52 birds/ha respectively on unmown, ungrazed plots.
A replicated, controlled study of four silage fields on separate dairy farms in England (Buckingham & Peach 2006) found that numbers of yellowhammer Emberiza citrinella, reed bunting Emberiza schoeniclus, wren Troglodytes troglodytes, song thrush Turdus philomelos and skylark Alauda arvensis were higher in plots left to set seed compared to mown plots, and in ungrazed seeded plots compared to grazed seeded plots. Significantly higher numbers of yellowhammer were observed in seeded plots (458 birds seen) compared to mown (one bird) and in ungrazed seeded plots (423) than grazed seeded plots (35). Reed buntings showed a similar response (seeded ungrazed: 160; grazed: 29; mown ungrazed: 3; grazed: 0). As did wren (seeded ungrazed: 22, grazed: 1; mown ungrazed: 2, grazed: 0) and song thrush (seeded ungrazed: 7, grazed: 3; mown ungrazed: 4, grazed: 0). There were more skylark in seeded than mown plots (18 vs. 0), and more in grazed (17) than ungrazed seeded plots (1). Two of four plots (0.5 ha) in each field were left uncut when the third silage cut was taken in July-August 2002 so that the grass set seed. One mown and one seeded plot was grazed by cattle until October, cattle were excluded from the other two plots. Numbers and species of birds using each plot were recorded over eight one hour periods between November 2002 and February 2003.
A review of four experiments on the effects of agri-environment measures on livestock farms in the UK (Buckingham et al. 2010) found that leaving rye grass Lolium perenne silage uncut was shown to benefit seed-eating birds in winter in one experiment. These are further results from a study discussed in Buckingham et al. (2004), with no reference given (Defra project BD1455). Only plots cut once during previous season produced large seed crops and attracted yellowhammers Emberiza citrinella (0.5 birds per visit on average) and reed buntings E. schoeniclus, (approximately 2 birds/visit on average) but not finches. Plots cut twice or three times (control) did not attract these birds. Birds were observed over two winters.
A replicated, controlled study on 12 farms in the West Midlands, UK (Defra 2009), in the winters of 2007-9, found that seed-eating birds (yellowhammer Emberiza citrinella and reed bunting E. schoeniclus) preferentially foraged in rye grass fields that were only one cut once for silage and ungrazed, compared to twice cut (ungrazed) or control (two or more cuts and grazed) plots. Meadow pipits Anthus pratensis (which eat seeds and insects) did not show a preference for perennial rye grass fields under different treatments and showed a weak preference for other rye grasses that were only cut once. Insect-eating winter wrens Troglodytes troglodytes preferentially foraged in all treatments except controls. Insect-eating European robins Erithacus rubecula preferentially foraged on control plots.
- Buckingham D.L., Atkinson P.W. & Rook A.J. (2004) Testing solutions in grass-dominated landscapes: a review of current research. Ibis, 146, 2-163
- Buckingham D.L. & Peach W.J. (2006) Leaving final-cut grass silage in situ overwinter as a seed resource for declining farmland birds. Biodiversity and Conservation, 15, 3827-3845
- Buckingham D.L, Atkinson P.W., Peel S. & Peach W. (2010) New conservation measures for birds on grassland and livestock farms. Proceedings of the Lowland Farmland Birds III: delivering solutions in an uncertain world, 60.
- Defra (2009) Grass silage as a new source of winter food for declining farmland birds. Defra Report report.