Background information and definitions
Cereal-based wholecrop silage (CBWCS) is an intervention that involves growing crops, not grass, to turn into silage. This may provide seed resources for grain-eating farmland birds throughout the year.
Supporting evidence from individual studies
A replicated, controlled trial in 2004-2006 in northwest England (Mortimer et al. 2007) found that seed-eating songbirds and swallows and martins were more abundant on cereal (wheat and barley) fields planted in livestock areas than in grass and maize fields. In winter 2005/6, 1,390-1,564 seed-eaters were recorded on barley stubbles compared to 48 on grass fields and 406 on maize. Large insect-eating birds (thrushes) were far more abundant on grass fields in winter (2,272 birds in total, compared to 28-789 on other field types. Winter wheat and spring barley were sown in 16 trial fields, each on a separate farm in Cheshire, Staffordshire and north Shropshire. Neighbouring maize or short-term grass silage fields were monitored for comparison. Plants, invertebrates and birds were monitored on each field, in summer 2005 and winter 2005/06.Study and other actions tested
A review of four experiments on the effects of agri-environment measures on livestock farms in the UK (Buckingham et al. 2010) found one study of CBWCS in which winter wheat planted for silage was avoided by seed-eating birds during winter, but used as much as a control spring barley crop during summer. Maize planted for silage was little used by birds in summer or winter. These results are reported in more detail by Peach et al. (2011). This study also describes the results of several other interventions, discussed in the relevant sections.Study and other actions tested
An update of Mortimer et al. 2007 included data from winter 2004/5 (Peach et al. 2011) and found that CBWCS fields were used significantly more by farmland birds than other crop types. Each farm contained two CBWCS fields (autumn-sown wheat, 5.3 ha, and spring-sown barley, 4.4 ha), one maize field (6.1 ha) and one grass field (2.1 ha). During summer, a total of 1,535 seed-eaters and 1,901 swallows and martins were found on barley CBWCS fields, compared with 847 and 197 for wheat CBWCS fields; 441 and 95 for maize fields; and 41 and 480 for grass fields. Northern lapwing Vanellus vanellus, insect-eating species, and crows did not use CBWCS fields more than other types in summer. In winter, seed-eating species (seed-eating songbirds, Eurasian skylark Alauda arvensis, meadow pipit Anthus pratensis) used barley stubbles extensively, whilst insect-eating species used other crop stubbles more. The authors argue that CBWCS (with selectively applied herbicide, retention of over-winter stubbles and delayed harvesting) offer a practical conservation measure for seed-eating farmland birds. This study uses data from Defra report number BD1448 (Defra 2007).Study and other actions tested