Action: Provide refuges during harvest or mowing
- Three studies examined the effect of providing refuges for birds during harvest or mowing in France and the UK. One replicated study in France found evidence that providing refuges during mowing reduced contact between mowing machinery and unfledged quail and corncrakes. However one replicated controlled study and a review from the UK found that Eurasian skylark did not use nesting refuges more than other areas.
During mowing and harvesting operations, ground‐nesting birds frequently remain in long grass or crops for as long as possible. If mowing/harvest occurs from the outside of the field inwards, this behaviour can leave the birds trapped in the centre of the field and killed as the last patch is harvested. However, if unharvested refuges are left in fields then it is possible that chicks and adults will remain in them and survive.
Supporting evidence from individual studies
A replicated study in 1996-1997 in 62 hay fields in Bourgogne, France (Broyer 2003) found that contact between mowing machinery and unfledged quail Cortunix cortunix and corncrakes Crex crex was reduced by approximately 50% and 33% respectively, by leaving 10 m-wide, uncut strips in the centre of fields. In addition, unmowed strips had the highest concentrations of corncrakes, quails and passerines (7.7 birds/ha, 3.8 birds/ha and 10.8 birds/ha respectively in 1996). All refuge areas were mown within the first 10 days of August using the ‘outside-in’ method. During mowing, observers with binoculars recorded birds in the refuge areas.
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 demonstrating that uncut nesting refuges for Eurasian skylark Alauda arvensis in silage fields were not used more than other areas. Refuge plots of 1 ha were cut with a raised mowing height in the first silage cut, then left uncut for the rest of the season. The plots were preferred for re-nesting for two weeks following the first cut, but subsequently did not have higher nest densities than other areas. Skylarks continually re-nest rather than re-nesting in a batch after each cut. After the second cut, safe areas were completely avoided by skylarks. This study formed part of a Defra-funded project (BD1454) as in (Defra 2010) for which no reference is given in the review.
A replicated controlled study in 2007 on seven fields in Dorset, UK (Defra 2010) found that after the first cut, Eurasian skylark Alauda arvensis did not nest in half hectare ‘safe nesting plots’ which were cut 10 cm higher than the rest of the field. Following the second cut of the main field, grass on safe nesting plots was avoided with new nesting attempts taking place on the surrounding cut grass. In 2007, 13 safe nesting plots were established on seven fields with skylark territories. Safe nesting plots were mown 10 cm higher during the first field cut (approximately 27 cm grass height on safe nesting plots vs 9 cm on normal cut areas), and were not mown at all during the second cut. They were left unmown/ungrazed until the end of August when skylark breeding had ceased.
- Broyer J. (2003) Unmown refuge areas and their influence on the survival of grassland birds in the Saône valley (France). Biodiversity and Conservation, 12, 1219-1237
- 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.