Action: Raise mowing height on grasslands to benefit farmland wildlife
- A replicated controlled study and a review from the UK found that raised mowing heights provided benefits to Eurasian skylark including increased productivity. A review found raised cutting heights were less damaging to amphibians and invertebrates.
- A randomized, replicated, controlled trial from the UK found that raising mowing height on grasslands had no effect on numbers of foraging birds or invertebrates. One replicated controlled study found no difference in invertebrate abundance.
- One replicated study from the UK found that northern lapwing and common starling chicks had greater foraging success in shorter grass.
Vegetation height is important in determining the value of a grassland to wildlife. High vegetation can provide more complex environments and more habitats, but short vegetation can allow birds access to the ground which can help foraging, and can reduce the risk of predation.
Supporting evidence from individual studies
A replicated study from January to May 2002 of 15 Northern lapwing Vanellus vanellus chicks on one grassland site in the Isle of Islay and 20 common starlings Sturnus vulgaris on one grassland site in Oxfordshire, UK (Devereux et al. 2004) found that both species experienced significantly greater foraging success in shorter grass. For lapwing chicks, foraging rate declined as grass height increased. Starlings spent 30% more time actively foraging and captured 33% more prey in short grass, although intake rate (captures per second of active foraging) did not differ between grass heights. Invertebrate abundance did not differ between long and short grass. Fertilizer application and water level was manipulated to provide a range of grass heights on the lapwing site. Starlings were observed in enclosures placed within intensively managed permanent pasture that was mown to either 3 cm (short grass) or 13 cm (tall grass).
A randomized, replicated, controlled trial from 2003 to 2006 on four farms in southwest England (Defra 2007) (same study as (Woodcock et al. 2007, Potts et al. 2009)) found that 50 x 10 m plots of permanent pasture cut to 10 cm in May and July did not attract more invertebrates or foraging birds than control plots cut to 5 cm. Plots were cut twice in May and July, and grazed in autumn/winter. There were twelve replicates of each management type, monitored over four years.
A randomised, replicated, controlled trial from 2003 to 2005 on four farms in southwest England (Woodcock et al. 2007) (same study as (Defra 2007, Potts et al. 2009)) found that 50 x 10 m plots of permanent pasture cut to 10 cm in May and July had similar numbers of beetles (Coleoptera) and beetle species to control plots cut to 5 cm. There were twelve replicates of each management type, monitored over three years.
A 2009 literature review (Humbert et al. 2009) found that cutting height has a large influence on mowing impact, with a raised cutting height being less damaging to field-dwelling animals. Three studies reported higher cutting heights were less damaging to invertebrates and amphibians (Löbbert et al. 1994, Classen et al. 1996, Oppermann et al. 2000).
Löbbert M., Kromer K.-H., Wieland C.C. (1994) Einfluss von Mäh- und Mulchgeräten auf die bodennahe Fauna [Influence of mowing and mulching equipment on ground fauna]. Pages 7–26 in: Forschungsberichte ‘‘Integrative Extensivierungs-und Naturschutzstrategien’’ H. 15. Universität Bonn, Institut für Landtechnik, Bonn.
Classen A., Hirler A., Oppermann R. (1996) Auswirkungen unterschiedlicher Mähgeräte auf die Wiesenfauna in Nordost-Polen [Effects of different mowing equipment on meadow fauna in northeast Poland]. Naturschutz und Landschaftsplanung, 28, 139–144.
Oppermann R., Handwerk J., Holsten M., & Krismann A. (2000) Naturverträgliche Mähtechnik für das Feuchtgrünland, Voruntersuchung für das E & E – Vorhaben [Nature-friendly mowing for wet grassland, preliminary study for E & E projects]. ILN Singen, Bonn.
A randomised, replicated, controlled trial from 2003 to 2006 in southwest England (Potts et al. 2009) (same study as (Defra 2007, Woodcock et al. 2007)) found plots of permanent pasture cut to 10 cm in May and July did not attract more butterflies (Lepidoptera), butterfly larvae or common bumblebees Bombus spp. than control plots cut to 5 cm. Experimental plots 50 x 10 m were established on permanent pastures (more than five-years-old) on four farms. There were nine different management types, with three replicates/farm, monitored over four years. Bumblebees and butterflies were surveyed along a 50 m transect line in the centre of each experimental plot, once a month from June to September annually. Butterfly larvae were sampled on two 10 m transects using a sweep net in April and June-September annually.
A 2010 review of four experiments on the effects of agri-environment measures on livestock farms in the UK (Buckingham et al. 2010) found one trial from 2006 to 2008 that tested the effect of mowing height on skylarks Alauda arvensis nesting in silage fields. Preliminary results showed that chick survival was not affected by raised cutting height. However, the number of new birds produced each year (productivity) was more sensitive to re-nesting rates than chick survival. Raised cutting height slightly increased productivity because skylarks re-nested sooner after cutting, but this was not enough to maintain a local population given survival rates. This study formed part of a Defra-funded project (BD1454) for which no reference is given in the review.
A replicated controlled study from 2006 to 2008 on silage fields in Dorset, UK (Defra 2010) found that raising the cutting height on grasslands benefited Eurasian skylark Alauda arvensis. Daily failure rates of skylark nests were lower and the likelihood of chicks fledging higher on fields with raised cutting heights (probability of chicks fledging in May: 0.6 vs 0.4 on high and low cut plots respectively). Annual skylark productivity on two-cut silage plots was higher when the first or both the first and second cuts were raised compared to normal low cuts (21 independent fledglings/100 pairs on plots where the first cut was raised, 24 where both cuts were raised vs four on plots where both cuts were low). Skylarks preferentially nested on raised cutting height plots in the two week period after mowing in both 2006 and 2007, and only nested in vegetation which was at least 10 cm tall. Invertebrate abundance was not significantly different between cutting heights. A split-plot set-up was used to test the effects of different mowing heights: average raised cutting height 12 cm, low cutting height approximately 6-7 cm (2006: 12 trial fields, 11 controls; 2007: eight trial, four controls). Entire fields were subject to raised or control mowing heights in 2008 (10 trial fields, 15 controls). All plots were cut using disc mowers. Skylark nests were monitored to assess daily productivity, and survival rates and chicks were radio-tagged to assess their survival after fledging. Stochastic simulation modelling was used to investigate the effects on skylark productivity.
- Devereux C.L., McKeever C.U., Benton T.G. & Whittingham M.J. (2004) The effect of sward height and drainage on Common Starlings Sturnus vulgaris and Northern Lapwings Vanellus vanellus foraging in grassland habitats. Ibis, 146, 115-122
- Defra (2007) Potential for enhancing biodiversity on intensive livestock farms (PEBIL). Defra report.
- Woodcock B.A., Potts S.G., Pilgrim E., Ramsay A.J., Tscheulin T., Parkinson A., Smith R.E.N., Gundrey A.L., Brown V.K. & Tallowin J.R. (2007) The potential of grass field margin management for enhancing beetle diversity in intensive livestock farms. Journal of Applied Ecology, 44, 60-69
- Humbert J.Y., Ghazoul J. & Walter T. (2009) Meadow harvesting techniques and their impacts on field fauna. Agriculture Ecosystems & Environment, 130, 1-8
- Potts S.G., Woodcock B.A., Roberts S.P.M., Tscheulin T., Pilgrim E.S., Brown V.K. & Tallowin J.R. (2009) Enhancing pollinator biodiversity in intensive grasslands. Journal of Applied Ecology, 46, 369-379
- 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 (2010) Modified management of agricultural grassland to promote in-field structural heterogeneity, invertebrates and bird populations in pastoral landscapes. Defra BD1454 report.