Plant wild bird seed or cover mixture
Overall effectiveness category Awaiting assessment
Number of studies: 7
Background information and definitions
Wild bird seed mixtures are commonly sown as part of agri-environment schemes aimed at restoring bird populations. Seed mixtures can contain a wide variety of plants, predominantly annual species, and are therefore re-sown every one or two years. Some commonly used plants may provide beneficial resources, in particular nectar, to butterflies and moths.
Wild bird seed mixes are normally composed of annual plants, as opposed to perennial species sown in nectar flower mixes (Pywell et al. 2008). For studies on sowing these mixes, see “Plant nectar flower mixture/wildflower strips”.
Pywell R., Hulmes L., Meek W. & Nowakowski M. (2008) Creation and Management of Pollen and Nectar Habitats on Farmland: Annual report 2007/8.
Supporting evidence from individual studies
A replicated, site comparison study in 2000 on a lowland arable farm in Leicestershire, UK (Moreby 2002, same experimental set-up as Moreby & Southway 2002) found that wild bird cover contained similar densities of caterpillars to in other field edge habitats. There was no difference in caterpillar densities between habitat types (data not presented). Ten edge habitats (first-year wild bird cover, second-year wild bird cover, non-rotational set-aside, beetle banks, brood cover, hedge bottoms, sheep-grazed pasture edges, ungrazed pasture edges, grass/wire fence lines and winter wheat headlands) were included in the study (sample size not given). Caterpillars were sampled with a vacuum suction sampler in June 2000 (no further details provided).Study and other actions tested
Referenced paperMoreby S.J. (2002) Permanent and temporary linear habitats as food sources for the young of farmland birds. Pages 327-332 in: D.E. Chamberlain (ed.) Avian Landscape Ecology: Pure and Applied Issues in the Large-Scale Ecology of Birds. International Association for Landscape Ecology (IALE(UK)), Aberdeen.
A replicated, site comparison study in 1995–1999 on an arable farm in Leicestershire, UK (Moreby & Southway 2002, same experimental set-up as 1 -Moreby 2002) found that the abundance of moth and butterfly caterpillars was similar in non-crop strips (wild bird cover or grass beetle banks) and crop fields in most years. The abundance of moth and butterfly caterpillars was similar in non-crop strips (0–1 individuals/sample) and crop fields (0–1 individuals/sample) in four out of five years. In 1996, the abundance of caterpillars was lower in non-crop strips (0.4 individuals/sample) than in crop fields (0–2.2 individuals/sample). However, a composite group of key ‘chick food insects’ (including caterpillars) had higher densities in non-crop strips (65 individuals/sample) than in crop fields (2–10 individuals/sample) in all years. Wild bird cover was sown as 2–5-m-wide strips along field boundaries and re-sown every few years with a cereal or kale-based Brassica spp. mixture. Grass beetle banks (1 m wide) were sown onto a raised bank along edges or across the centre of fields. Invertebrates were sampled each year in the centre of 5–11 wild bird cover strips or grass beetle banks, and 3-m into 3–4 pasture, 8–12 wheat, 6–8 barley, 3–6 oilseed rape and 4 field bean fields. Two samples of 0.5 m² were taken in each habitat using a D-Vac suction sampler in June 1995–1999.Study and other actions tested
A replicated, controlled study in 2004–2005 on four arable farms in southern England, UK (Pywell et al. 2007) found that sown wild bird seed mix plots had a higher abundance and species richness of butterflies than wheat crop. The abundance and species richness of butterflies were higher in the wild bird mix plots than in the crop (data not presented). In April 2004 and 2005, a seed mix containing white millet Echinochloa esculenta, linseed Linum usitatissimum, radish Raphanus sativus and quinoa Chenopodium quinoa was sown in a 150 × 30 m patch in the centre of an arable field (winter wheat) on each of four farms in Cambridgeshire, Bedfordshire, Oxfordshire and Buckinghamshire. Butterflies were counted in each patch in summer 2005.Study and other actions tested
A replicated, randomized, controlled study in 2006–2007 on a farm in Warwickshire, UK (Pywell et al. 2008) found that butterfly abundance and species richness differed between 10 plant species commonly sown in wild bird seed mixtures. In 2006, more butterflies were found in plots sown with lucerne Medicago sativa (6.3 individuals/plot) than plots sown with borage Borago officinalis (0.3 individuals/plot), chicory Cichorium intybus (0.8 individuals/plot) and sainfoin Onobrychis viciifolia (0.8 individuals/plot). More butterfly species were found in lucerne plots (3.5 species/plot) than in borage, chicory, sainfoin and fodder radish Raphanus sativus (0.3–0.5 species/plot). There was no significant difference in abundance (1.0–3.3 individuals/plot) or species richness (1.0–2.8 species/plot) between the other plant species. In 2007, red clover Trifolium pratense had a higher abundance of butterflies (3.3 individuals/plot) than chicory (0.0 individuals/plot), but the abundance on all other plant species was similar (0.3–2.3 individuals/plot) and there were no significant differences in species richness (0.0–1.8 species/plot). In May 2006, ten small-seeded crop species commonly sown in wild bird seed mixtures (borage, buckwheat Fagopyrum esculentum, crimson clover Trifolium incarnatum, fodder radish, linseed Linum usitatissimum, lucerne, mustard Brassica juncea, phacelia Phacelia tanacetifolia, sunflower Helianthus annuus and sweet clover Melilotus officinalis) and three perennial species sown in pollen and nectar mixtures (chicory, red clover, sainfoin) were sown individually in 6 × 4 m plots, replicated four times. Annual species were re-sown May 2007. Butterflies were surveyed six times/year, from July–September 2006 and May–September 2007.Study and other actions tested
A replicated, randomized, controlled study in 2002–2006 on four lowland farms in Devon and Somerset, UK (Potts et al. 2009) found that plots sown annually with mixes including wild bird seed had a higher abundance and species richness of butterflies, but a lower abundance of caterpillars, than grassland plots. In the first two years, plots sown with wild bird seed mixes had a higher abundance (4–10 individuals/transect) and species richness (2–4 species/transect) of adult butterflies than extensively (abundance: 3–5 individuals/transect; richness: 2 species/transect) or conventionally managed (abundance: 1–2 individuals/transect; richness: 1 species/transect) grassland. However, there were fewer caterpillars in the sown plots (0–3 caterpillars/transect) than the extensively (1–8 caterpillars/transect) or conventionally managed (0–7 caterpillars/transect) grassland. In April 2002, experimental plots (50 × 10 m) were established on permanent pastures (>5-years-old) on four farms. There were nine treatments, with three replicates/farm. Two sown treatments comprised a mix of six crops and four legumes, or barley Hordeum vulgare undersown with seven grasses and five legumes. Two extensive grassland treatments had minimal disturbance during summer and five conventional grassland treatments included modifications to conventional silage management (reducing fertilizer application, cutting and grazing). From June–September 2003–2006, butterflies were surveyed once/month on a 50-m transect through the centre of each plot. In April, June, July and September 2003–2006, caterpillars were counted (but not identified) on two 10-m transects/plot using a sweep net (20 sweeps/transect).Study and other actions tested
A replicated, randomized, paired, controlled study in 2005–2011 on an arable farm in Buckinghamshire, UK (Heard et al 2011) found that land managed under an agri-environment scheme, including sowing wild bird seed mixtures, had a higher abundance, but not species richness, of butterflies and micro-moths than conventional farming, but there was no difference in abundance or species richness of other moths. Butterfly abundance was higher under enhanced Entry-Level Stewardship (ELS) (5,400 individuals/60 ha) and standard ELS (2,000 individuals/60 ha) than under conventional farming (1,400 individuals/60 ha). Micro-moth abundance was also higher under enhanced ELS (79 individuals) than standard ELS (32 individuals) or conventional farming (20 individuals). However, the abundance of macro-moths and threatened moths was similar under enhanced ELS (macro: 126; threatened: 6 individuals), standard ELS (macro: 79; threatened: 5 individuals) and conventional farming (macro: 79; threatened: 6 individuals). Species richness of all groups was similar under enhanced ELS (macro: 20; micro: 11; threatened: 3 species), standard ELS (macro: 20; micro: 8; threatened: 2 species) and conventional farming (macro: 18; micro: 5; threatened: 2 species) (butterfly data not presented). In 2005, a 1,000-ha farm was divided into five 180-ha blocks. Three 60-ha areas/block were assigned to three treatments: enhanced ELS (5% land removed from production, three 0.5-ha winter bird food patches sown); standard ELS (1% land removed from production, one 0.25-ha winter bird food patch sown); conventional farming (no winter bird food patches) (see paper for other details). From May–August 2006–2011, butterflies were recorded four times/year on one 50-m transect/60-ha area, passing through all available habitats. In late-May 2007–2011 and late-July 2006–2011 moths were surveyed using Robinson light traps. One block was surveyed/night, with one trap/treatment.Study and other actions tested
Referenced paperHeard M.S., Botham M., Broughton R., Carvell C., Hinsley S., Woodcock B., Pywell R.F., Amy S., Bellamy P.E., Hill R.A., Hulmes S., Hulmes L., Meek W.R., Nowakowski M., Peyton J., Redhead J.W., Shore R.F. & Turk A. (2011) Quantifying the effects of Entry Level Stewardship (ELS) on biodiversity at the farm scale: The Hillesden Experiment. Natural England report, CEH report to Natural England, no. MA01031 (Project:RP00026).
A replicated, randomized, controlled study in 2007–2010 on 28 arable farms in Wessex and East Anglia, UK (Holland et al. 2015) found that farms with enhanced agri-environment scheme (AES) habitats, including areas of wild bird seed mixture, had a higher abundance of some butterfly species than farms with simpler AES habitats. In early summer, farms with enhanced AES habitats had a higher abundance of blue (Lycaenidae: 0.05 individuals/100 m) and white (Pieridae: 0.46 individuals/100 m) butterflies along boundaries than farms with Entry Level Scheme (ELS) habitats (blues: 0.04; whites 0.21 individuals/100 m), but a lower abundance of skippers (Hesperiidae) in the AES habitat itself (enhanced: 0.00; ELS: 0.02 individuals/100 m). In mid-summer, enhanced AES farms had a higher abundance of white butterflies (0.69 individuals/100 m), but a lower abundance of brown butterflies (Satyridae: 0.16 individuals/100 m) in the AES habitat, and a lower abundance of blue butterflies (0.05 individuals/100 m) along boundaries than ELS farms (whites: 0.38; browns: 0.49; blues: 0.11 individuals/100 m). In spring 2007, twenty-four farms (12 in East Anglia and 12 in Wessex) were randomly assigned to two treatments: 16 farms with enhanced AES habitat (1.5–6.0 ha of wild bird seed mixes, floristically-enhanced grass mixes, wildflower strips and natural regeneration by annual cultivation); and eight farms with ELS habitat (1.5–6.0 ha of grass margins and game cover (usually maize)). Two additional ELS farms/region, already managed organically with 1.5 ha of ELS habitat, were also studied. From 2008–2010, butterflies were surveyed twice/year on 11 fixed 100-m transects, in mid-May–mid-June and mid-July–early August. Eight transects/site were located in AES habitat, and three transects/site were located on field boundaries away from the AES habitat.Study and other actions tested