Action: Create skylark plots
- All four studies from the UK and Switzerland (two replicated and controlled, and one review) investigating the effect of skylark plots on Eurasian skylarks, found a positive effect, reporting increases in skylark population size, breeding density, duration or success or a lower likelihood of skylarks abandoning their territory relative to fields without plots. A replicated study from Denmark found that skylarks used undrilled patches within cereal fields more than expected by an even distribution across the landscape.
- Four studies reported the effect of undrilled patches on wildlife other than skylarks. Three studies from the UK (including two replicated studies, of which one also controlled and a review) found benefits to plants and invertebrates. Whilst two studies (both replicated, one also controlled) from the UK found no significant differences in the number of some invertebrates or seed-eating songbirds between skylark plots and conventional crop fields.
- One replicated study from the UK investigated different skylark plot establishment techniques. Plots that were undrilled had greater vegetation cover and height than plots established by spraying out with herbicide.
Eurasian skylarks Alauda arvensis require short vegetation to nest in. Skylark plots are small (usually 4-16 m2) undrilled patches within cereal fields which provide this short vegetation, with little impact on overall productivity. They are similar to lapwing plots (see ‘Leave uncropped, cultivated margins or plots (includes ‘lapwing plots’)) but much smaller.
Supporting evidence from individual studies
A replicated study from April-May 1990 to 1993 in five spring-sown barley fields in eastern Jutland, Denmark (Odderskær et al. 1997) found that Eurasian skylarks Alauda arvensis used unsown plots in the fields significantly more than expected by an even distribution across the landscape. Radio-tracked birds were observed more in tramlines and unsown plots and mean dropping density was significantly higher in unsown areas than in crops (1.4 droppings/ha vs 0.1). One 22 ha field with one hundred 40 m2 plots had higher densities of skylarks than four fields with an average of seven plots/ha, each of 7 m2. Tramlines (30 cm wide, 18 m apart) were kept clear of vegetation by driving a truck along them several times a week. Adult male and female skylarks were radio-tracked and observed visually. Dropping counts were made in two 5 x 5 m squares in eight territories in one field (May and June 1991).
A replicated, controlled study from April-August in 2002-2003 in 15 sites in northern, eastern and southern England (Morris et al. 2004) found that Eurasian skylark Alauda arvensis breeding density, duration and success were higher in winter wheat fields with undrilled patches (4 x 4 m) than in fields with widely-spaced (25 cm apart) rows or under conventional management (0.3 nests/ha in fields with undrilled plots vs 0.2 for the other treatments). Fields with undrilled patches also lost fewer territorial and nesting birds over the breeding season and by the end of the breeding season nests in these fields produced an average of one more chick than control nests. Body condition of nestlings decreased in control nests over the breeding season but increased in experimental fields. The proportion of within-treatment foraging flights remained constant in fields with undrilled patches but decreased over time in other treatments. Three treatments were surveyed: winter wheat sown in wide-spaced rows, undrilled patches with a density of 2 patches/ha, and conventional control winter wheat fields. Skylarks were surveyed from April to mid-August, with the number of territorial males, nests, nest productivity, nestling body condition and foraging locations recorded. Ten of the sites were part of the same replicated, controlled study (SAFFIE – Sustainable Arable Farming For an Improved Environment) as Ogilvy et al. 2006, Smith & Jones 2007, Smith et al. 2009.
A before-and-after study from 2000 to 2005 in Cambridgeshire, England (Donald & Morris 2005), found that the population of Eurasian skylarks Alauda arvensis on an arable farm increased from 10 territorial males in 2000 to 34 in 2005, following the introduction of skylark plots in 2001 (in addition to 6 m margins around fields and set-aside). Nests were also aggregated in fields with skylark plots. The study also reports that fields on 15 experimental farms with skylark plots had 30% more skylarks than control fields. In addition, nests in fields with skylark plots produced 0.5 more chicks/breeding attempt. Skylark plots 4 x 4 m were established at a density of 2 plots/ha. This study was part of the SAFFIE – Sustainable Arable Farming For an Improved Environment research project.
A replicated, controlled study in 2002-2003 on ten farms in England (Ogilvy et al. 2006) found that 45% of 159 Eurasian skylark Alauda arvensis nests monitored were found in fields with skylark plots. By June, fields with skylark plots had 30% more skylarks and 100% more nests than control winter wheat fields with normal row spacing. At the start of the breeding season there was little difference in success between treatments, but by June, fields with skylark plots had more nests (1 nest/ha vs 0.4) and more chicks/nest than controls (1.75 chicks/nest vs 0.9). Over the whole season, nests in experimental fields raised 0.5 more chicks than controls and 1.5 more chicks than controls late in the season. Plots had significantly higher undesirable weed cover than surrounding crop (6% vs 4% weed cover), although cover in the field as a whole was no higher (2% vs 1.5%). In 2002, but not 2003, invertebrate species richness and abundance were higher in fields with patches, compared to controls. Invertebrates, plants and skylarks were monitored. This study was part of the same replicated, controlled study (SAFFIE – Sustainable Arable Farming For an Improved Environment) as Morris et al. 2004, Smith & Jones 2007, Smith et al. 2009.
A 2007 review of published and unpublished literature (Fisher et al. 2007) found one study (Ogilvy et al. 2006) with experimental evidence of the benefits of skylark plots to plants (although undesirable plant species prevalent) and invertebrates (invertebrate abundance higher in the surrounding crop).
A replicated, controlled study in 2002 and 2003 at ten sites in England (Smith & Jones 2007) found that plant species richness and arthropod species richness in one of two years were higher in wheat fields with undrilled patches than control fields. Weed and crop cover did not differ significantly between treatments (weeds: 1-2%; crops: 33-55%), but plant species richness was higher in fields with undrilled patches (11 species) than control fields (7 species). Weed cover and species richness were also significantly higher on undrilled patches (1-22% cover; 9-10 species) than the surrounding field (1-4%; 5-8 species). In 2002, arthropod species richness and rove beetle (Staphylinidae) abundance were higher in fields with patches than control fields (10 vs 6 arthropod species; 9 vs 6 rove beetles), there was no difference in 2003. In 2002, wolf spiders (Lycosidae) were more abundant in undrilled patches than the surrounding field (1.1 vs 0.4 individuals), whereas the opposite was true for rove beetle abundance (4 vs 9 individuals), species richness (4 vs. 6 species) and in 2003 abundance of ground active invertebrates (0.3 vs 104 individuals). In 2002, arthropod abundance was higher in the surrounding fields than undrilled patches in May (23 vs 16 individuals), but higher in undrilled patches than surrounding fields in July (53 vs 36). Undrilled patches (4 x 4 m) were created at a density of 2 patches/ha in an otherwise conventionally managed crop. Vegetation composition was sampled in 24 quadrats (0.25 m²) in May and July 2002 and 2003. Arthropods were sampled in the same locations using D-Vac suction sampling in May, June, and July and in pitfall traps for 7 days in June. This study was part of the same replicated, controlled study (SAFFIE – Sustainable Arable Farming For an Improved Environment) as Morris et al. 2004, Ogilvy et al. 2006, Smith et al. 2009.
A 2007 study and literature review (Stoate & Moorcroft 2007) reports that Eurasian skylarks Alauda arvensis were able to raise 49% more young in fields with skylark plots, compared to fields without plots, by prolonging the length of the breeding season.
A replicated study of skylark plot establishment in two wheat fields in 2008-2009 in Cambridgeshire, UK (Dillon et al. 2009) found that plots left undrilled had greater vegetation cover than those established by spraying out with herbicide. Vegetation cover within sprayed plots (sprayed out in December, January or February) tended to remain very low (<30%), particularly in February-sprayed plots (<10%), undrilled plots had 54% cover in July. Increase in cover in undrilled plots was related to a greater abundance of crop (May 5%, July 8%) and blackgrass Alopecurus myosuroides (May 10%, July 40%). Cover of both crop and blackgrass remained low in all sprayed treatments (blackgrass: < 5%; crop: <2%). Plots following spring beans tended to have greater vegetation cover than those following oilseed rape. Undrilled plots had significantly taller vegetation (17-29 cm) than sprayed plots (July: 2-13 cm). A total of 56-65 plots were established/year by leaving them undrilled during wheat drilling, or by spraying out using a glyphosate herbicide until the density of plots was at least 2 plots/ha. Presence of bare ground, crop, blackgrass and charlock Sinapis arvensis were sampled in May, June and July in ten 0.25 m² quadrats/plot. Maximum vegetation height was also recorded in June and July.
A replicated, controlled study from March-July 2006 in mixed farmland near Berne, Switzerland (Fischer et al. 2009) found that Eurasian skylarks Alauda arvensis with territories that included undrilled patches were significantly less likely to abandon their territory than birds without patches, and more likely to use the undrilled patches as nesting and foraging sites. Use of winter wheat fields by skylarks changed through the breeding season; from June to July, the percentage of control fields (without undrilled plots) in skylark territories decreased from 60% to 38%, whilst the percentage of undrilled patches in skylark territories remained approximately 55% from May to July. Nest productivity was identical between control areas and fields with undrilled patches (1.4 chicks/territory) and there was no difference in chick body mass or tarsus length. Undrilled patches were composed of either four 3 x 12 m patches/ha (in seven fields) or a single strip 2.5 ? 80 m (in 14 fields). In autumn 2005 undrilled patches were sown with six annual weed species including common corncockle Agrostemma githago in winter wheat fields. Skylark territories were surveyed over one breeding season (2006) in 21 experimental sites and 16 control wheat fields.
A replicated, controlled study from April-August in 2002 and 2003 on 10 farms in northern and eastern England (Smith et al. 2009) found that invertebrate abundance in undrilled patch fields was not significantly different from conventional (control) winter wheat fields. In 2002, mean invertebrate species richness in undrilled patch fields was 9.8 compared to 6.4 in control fields. There were no significant differences in 2003, possibly because weed cover was 50% lower than 2002. Within undrilled patch fields, rove beetle (Staphylinidae) abundance and species richness was higher in crop areas while money spider (Lycosidae) and herbivorous invertebrate species were more abundant in the undrilled patches. There were no significant differences in faecal content between Eurasian skylark nestlings in treatment or control fields. The authors suggest that a critical threshold of weedy cover must be reached before any significant effect on invertebrates is detected. Three treatments were established on each farm: undrilled patches (4 x 4 m) with a density of 2 patches/ha, winter wheat sown in wide-spaced rows (25 cm apart) and conventional control winter wheat fields. Invertebrates were sampled using vacuum sampling (May, June, July) and pitfall traps (June). Plants were surveyed in twenty-four 0.25 m2 quadrats in May and July. Skylark droppings were collected from nestlings, fledglings and adults for faecal analysis, April-September 2002-2003. This study was part of the same replicated, controlled study (SAFFIE – Sustainable Arable Farming For an Improved Environment) as Morris et al. 2004, Ogilvy et al. 2006, Smith & Jones 2007.
A replicated site comparison study in winter 2007-2008 and summers 2008 and 2009 on farms in three English regions (Field et al. 2010) found that skylark plots were well used (1-3 seed-eating farmland songbirds/ha) but did not have significantly more birds than crop fields or fallow plots. Surveys were carried out on 69 farms with Higher Level Stewardship in East Anglia, the West Midlands or the Cotswolds and 31 farms across all three regions with no environmental stewardship. Flush transects were used to record as many birds as possible.
- Odderskær P., Prang A., Poulsen J., Andersen P. & Elmegaard N. (1997) Skylark (Alauda arvensis) utilisation of micro-habitats in spring barley fields. Agriculture, Ecosystems & Environment, 62, 21-29
- Morris A.J., Holland J.M., Smith B. & Jones N.E. (2004) Sustainable Arable Farming For an Improved Environment (SAFFIE): managing winter wheat sward structure for Skylarks Alauda arvensis. Ibis, 146, s155-162
- Donald P.F. & Morris T.J. (2005) Saving the sky lark: new solutions for a declining farmland bird. British Birds, 98, 570-578
- Ogilvy S.E., Clarke J.H., Wiltshire J.J.J., Harris D., Morris A. & Jones N. (2006) SAFFIE - research into practice and policy. Proceedings of the HGCA Conference, Arable crop protection in the balance: Profit and the environment, 14.1-14.12.
- Fisher G.P., MacDonald M.A. & Anderson G.Q.A. (2007) Do agri-environment measures for birds on arable land deliver for other taxa? Aspects of Applied Biology, 81, 213-219
- Smith B. & Jones N.E. (2007) Effects of manipulating crop architecture on weed and arthropod diversity in winter wheat. Aspects of Applied Biology, 81, 31-38
- Stoate C. & Moorcroft D. (2007) Research-based conservation at the farm scale: development and assessment of agri-environment scheme options. Aspects of Applied Biology, 81, 161-168
- Dillon I.A., Morris A.J., Bailey C.M. & Uney G. (2009) Assessing the vegetation response to differing establishment methods of Skylark Plots in winter wheat at Grange Farm, Cambridgeshire, England. Conservation Evidence, 6, 89-97
- Fischer J., Jenny M. & Jenni L. (2009) Suitability of patches and in-field strips for sky larks Alauda arvensis in a small-parcelled mixed farming area. Bird Study, 56, 34-42
- Smith B., Holland J., Jones N., Moreby S., Morris A.J. & Southway S. (2009) Enhancing invertebrate food resources for skylarks in cereal ecosystems: how useful are in-crop agri-environment scheme management options? Journal of Applied Ecology, 46, 692-702
- Field R.H., Morris A.J., Grice P.V. & Cooke A.I. (2010) Evaluating the English Higher Level Stewardship scheme for farmland birds. Aspects of Applied Biology, 100, 59-68