Action: Pay farmers to cover the costs of bird conservation measures
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- Three reviews from the UK of three studies captured reported population increases of three species after the introduction of specially-designed agri-environment schemes. These species were cirl buntings, corncrakes and Eurasian thick-knees. One of these found that many other species continued to decline.
- Twenty-two of 25 studies all from Europe, including a systematic review, examining local population levels or densities found that at least some birds studied were at higher densities, had higher population levels or more positive population trends on sites with agri-environment schemes, compared to non-agri-environment scheme sites. Some studies found that differences were present in all seasons, others in either summer or winter. Fifteen studies from Europe, including a systematic review, found that some or all species were not found at higher densities, had similar or lower population levels, showed similar population trends on sites with agri-environment schemes, compared with non-agri-environment scheme sites, or showed negative population trends. A study from the Netherlands found that many agri-environment scheme farms were sited in areas where they were unlikely to be effective.
- One small study from the UK found no differences between winter densities of seed-eating birds on UK Higher Levels Stewardship sites, compared with those under Entry Level Stewardship.
- A replicated study from the UK found that grey partridge survival was higher on agri-environment scheme sites than non-scheme sites. This difference was not significant every year.
- Two of three studies investigating reproductive productivity, including one replicated study, found that productivity was higher on farms under agri-environment schemes. One replicated study from the UK found no effect of agri-environment schemes on productivity.
- A review (Vickery et al. 2010) found that the amount of land entering an agri-environment scheme was on target, but that some options were not being used at high enough rates to help many species.
Agri-environment schemes are government or inter-governmental schemes designed to compensate farmers financially for changing agricultural practice to be more favourable to biodiversity and landscape. In Europe, agri-environment schemes are an integral part of the European Common Agricultural Policy (CAP) and Member States devise their own agri-environment prescriptions to suit their agricultural economies and environmental contexts.
Agri-environment schemes represent many different specific interventions, and where a study’s results can be clearly assigned to a specific intervention, they appear in the appropriate section. This section, meanwhile, includes evidence about the success of agri-environment policies overall.
Evidence relating to the Swiss Ecological Compensation Areas is placed under ‘Increase the proportion of natural habitat in the landscape’, if it involves monitoring biodiversity effects on a landscape scale, rather than focussing on specific aspects of habitat management.
In the USA and Canada, schemes such as the Conservation Reserve Program (USA) and the Permanent Cover Program (Canada) are aimed primarily at creating semi-natural and natural vegetation and are mainly discussed in ‘Habitat creation and restoration’.
Supporting evidence from individual studies
A 1998 literature review (Ovenden et al. 1998) found that cirl buntings Emberiza cirlus in Britain responded positively to Countryside Stewardship Schemes, reaching population levels of 360-388 occupied territories in 1995- 1997, compared with 118 or so in the mid-1980s. Some of the interventions used include reducing grassland management intensity; sowing arable field margins; managing hedgerows for wildlife; growing spring barley; reducing herbicide use and maintaining overwinter stubbles. More studies describing the effects of these interventions are discussed in the relevant sections.
A 2000 literature review from the UK (Aebischer et al. 2000) found that the populations of four farmland birds (grey partridge Perdix perdix, cirl buntings Emberiza cirlus, corncrake Crex crex and Eurasian thick-knee Burhinus oedicnemus) increased following agri-environment schemes targeted at them. The individual schemes are discussed in the relevant interventions.
A 2001 replicated paired site comparison study in south Devon, England (Peach et al. 2001) found that the number of cirl bunting Emberiza cirlus increased significantly more (up 72%, from 54 to 93 breeding territories) in areas participating in the Countryside Stewardship Scheme, than on adjacent land not participating in the Countryside Stewardship Scheme (down 20%, from 124 to 96 territories) between 1992 and 1999. Countryside Stewardship Scheme land that was near to known bunting breeding territories saw greater increases in bunting numbers than Countryside Stewardship Scheme areas further away: of the nine agreements further than 2 km from the nearest known breeding site in 1992, seven remained un-colonised in 1999, one lost its only pair and one gained a pair. Forty-one 4 km² squares containing both land within the Countryside Stewardship Scheme and non-Countryside Stewardship Scheme land were surveyed in 1992, 1998 and 1999. In each year each tetrad was surveyed at least twice, the first time during mid April to late May, and the second time between early June and the end of August.
A replicated 2002 study from nine areas of the UK under Environmentally Sensitive Areas schemes (DEFRA 2003) found that the impacts of Environmentally Sensitive Area designation on farmland birds were mixed. There was evidence for population increases or high numbers of some species of birds on Environmentally Sensitive Areas-managed land for four Environmentally Sensitive Areas. Populations of some species were stable in six Environmentally Sensitive Areas, often in contrast to national trends, but four Environmentally Sensitive Areas saw falls in the populations of at least one target species. The authors also note that in five regions there were not adequate data for all target species. The Environmentally Sensitive Areas scheme was introduced in 1987 and offered payments for either maintaining or enhancing landscape quality and biodiversity.
A study in 1997 in two Environmentally Sensitive Areas in eastern England (Ausden & Hirons 2002) found that higher tier options (i.e. those with more demanding prescriptions but higher financial compensation) held significantly higher densities of wading birds (northern lapwing Vanellus vanellus, common redshank Tringa totanus and common snipe Gallinago gallinago) than lower tiers (Tier 1: 0.02-0.04 pairs/ha; Tier 2: 0.07-0.22; Tier 3: 0.40). In addition, they held more waders for each unit of money spent on the Environmentally Sensitive Area (Tier 1: 18-46 pairs/£100,000; Tier 2: 29-114; Tier 3: 167). However, when examining 1988-1997 population trends in four Environmentally Sensitive Areas, the authors found all three species investigated declined significantly (lapwing: 0.7-13% decline each year; redshank: 1.8-18.6%; snipe: 7.3-29.7%). The impact of wetland protection and management on waders is discussed in ‘Maintain traditional water meadows’ and ‘Legally protect habitats’.
A review of research on agri-environment schemes in the UK (Evans et al. 2002) summarised two reports (Wilson et al. 2000, ADAS 2001) evaluating the effects of the Arable Stewardship Pilot Scheme (ASPS) in two regions (East Anglia and the West Midlands) from 1998-2003. At the whole farm scale in winter, seed-eating songbirds, thrushes and wagtails showed some increase on agreement farms relative to control farms (numbers not given). In summer, numbers of breeding northern lapwing Vanellus vanellus, reed bunting Emberiza schoeniclus, greenfinch Carduelis chloris, house sparrow Passer domesticus, common starling Sturnus vulgaris and yellow wagtail Motacilla flava were higher on agreement farms. Agreement farms had some of the following options: overwinter stubbles (sometimes preceded by reduced herbicide, followed by fallow or a spring crop), undersown spring cereals (sometimes followed by a grass or grass/clover ley), arable crop margins with reduced spraying (conservation headlands), grass margins or beetle banks and sown wildlife seed mixtures (pollen and nectar or wild bird seed mix). Over-winter stubble (974 and 2200 ha in East Anglia and West Midlands respectively) and conservation headlands (605 and 1085 ha in East Anglia and West Midlands respectively) were the most widely implemented options. The effects of the pilot scheme on birds were monitored at the farm scale over three years, relative to control areas, or control farms.
A 2003 replicated site comparison study of 102 fields across East Anglia and the West Midlands in the UK (Bradbury & Allen 2003), found that two years after the introduction of the Arable Stewardship Scheme there was no difference in the number of farmland bird species observed in winter on Arable Stewardship Scheme and non-Arable Stewardship Scheme fields. There were, however, significantly more seed-eating songbirds, wagtails, and pipits on fields participating in the scheme than on farms not participating in the scheme. A further survey of 98 fields in summer found that although there were significantly more northern lapwings, starlings, greenfinches and reed buntings on Arable Stewardship Scheme fields, there were also fewer woodpigeons Columba palumbus, sedge warblers Acrocephalus schoenobaenus and rooks Corvus frugilegus than on the non-Arable Stewardship Scheme fields. Fifty-four Arable Stewardship Schemes and 48 comparable non- Arable Stewardship Scheme fields were surveyed for farmland birds in both the winters of 1998/1999 and 1999/2000; 50 Arable Stewardship Schemes and 48 non- Arable Stewardship Scheme fields were surveyed in the summer months of 1999 and 2000. The seed-eating songbirds identified included 13 species of finches, buntings and sparrows; wagtails and pipits comprised three species.
A 2003 replicated site comparison study of 76 farms in East Anglia, UK, and the West Midlands (Browne & Aebischer 2003) found that autumn densities of grey partridges fell across both Arable Stewardship Pilot Scheme and non-Arable Stewardship Pilot Scheme farms from 1998 (when Arable Stewardship Pilot Scheme was introduced) to 2002. In East Anglia densities fell 68% on non-ASPS farms (5.5 to 1.8 birds/km²) and 21% on Arable Stewardship Pilot Scheme farms (9.6 to 7.6 birds/km²); in the West Midlands densities fell 40% on non-ASPS farms (1.4 to 0.8 birds/km²) and 78% on Arable Stewardship Pilot Scheme farms (3.0 to 0.8 birds/km²). In East Anglia, however, the young-to-old ratio doubled on Arable Stewardship Pilot Scheme plots from 1998 to 2002 (1 to 2 young : adult birds), whereas on non-Arable Stewardship Pilot Scheme farms the ratio fell by more than 50% (1.2 to 0.5 young : adult birds), indicating that the change in productivity on Arable Stewardship Pilot Scheme farms was twice that on non-Arable Stewardship Pilot Scheme farms. Surveys of grey partridge were made once each autumn in 1998 and 2002 on 76 farms: 20 ASPS and 19 non-ASPS farms in East Anglia and 20 Arable Stewardship Pilot Schemes and 17 non-Arable Stewardship Pilot Scheme farms in the West Midlands.
A 2003 review of 29 studies from six European countries (Kleijn & Sutherland 2003) found that agri-environment schemes had no consistent effect on bird species. While there were individual successes, such as the 83% increase in cirl bunting between 1992 and 1998 on land within the Countryside Stewardship Scheme compared with the 2% increase on adjacent land not in the scheme, only 13/29 studies found agri-environment schemes increased bird species richness or abundance. Two studies reported negative effects and nine reported both positive and negative effects. Of the 19 studies that involved statistical tests, only four found positive effects, 2 of 19 reported negative effects and 9 of 19 reported both positive and negative effects.
A 2004 review of agri-environment scheme uptake and effectiveness in Europe (Berendse et al. 2004) found that an average of 9% of agricultural land in EU countries was under agri-environment scheme designation, but that this ranged from 7% or less in some countries (e.g. The Netherlands, Spain, Greece) to 78, 77 and 64% in Austria, Finland and Sweden, respectively. In the UK, four rare species (grey partridge, corncrake, stone curlew or Eurasian thick-knee and cirl bunting) benefited from agri-environment schemes, although the authors note that densities of some species were higher on agri-environment scheme farms before they were designated. Similar methodological issues were found with studies in the Netherlands, where studies found that, at both field and larger scales, there were no population-level benefits of agri-environment scheme designation, although hatching and fledging rates of some species were higher on agri-environment scheme farms.
A 2004 replicated site comparison study of 74 farms in East Anglia and the West Midlands (Bradbury et al. 2004) found few differences in the density of farmland birds on farms participating in the Arable Stewardship Pilot Scheme and non-Arable Stewardship Pilot Scheme and, five years after the introduction of the scheme. In the West Midlands, although seed-eating songbirds, wagtails and pipits, insectivores, and raptors were found at higher densities on Arable Stewardship Pilot Scheme land than non-Arable Stewardship Pilot Scheme land, these higher densities were already present when measured within one year of the introduction of the scheme. Moreover, in East Anglia there were no differences the bird densities found on Arable Stewardship Pilot Schemes and non-Arable Stewardship Pilot Scheme fields. Surveys of grey partridge populations on 76 farms in 1998 and 2002 found that adult densities decreased uniformly on both Arable Stewardship Pilot Schemes and non- Arable Stewardship Pilot Scheme farms over the five-year period. Bird surveys were carried out twice each during the winters of 1998/1999 and 2002/1903 on 18 Arable Stewardship Pilot Scheme and 19 non-Arable Stewardship Pilot Scheme farms in East Anglia and 19 Arable Stewardship Pilot Schemes and 18 non-Arable Stewardship Pilot Scheme farms in the West Midlands.
A 2004 literature review of farmland bird declines in Britain (Newton 2004) found that 12 of 30 declining species have shown local population density increases after the implementation of agri-environment scheme options. Five out of ten seed-eating birds responded positively to agri-environment schemes, one (cirl bunting) showing large increases. Three other songbirds as well as corncrake, grey partridge and two waders responded to agri-environment scheme options. A further seven species responded to local conservation measures and eleven species were not studied sufficiently, were found not to respond to conservation measures or were recovering following national legislation (i.e. the prohibition of organochlorine pesticides).
A 2004 literature review (Vickery et al. 2004) describes how ten years of agri-environment schemes in the UK have failed to halt the decline of many formerly common farmland species. However, it also points out that specially-designed agri-environment scheme options have led to local-scale population increases of three rare and range-restricted species (corncrake, Eurasian thick-knee and cirl bunting).
A 2006 replicated site comparison study in Spain and the Netherlands (Kleijn et al. 2006) found that birds bred more often, or were more numerous in areas participating in two agri-environment schemes, than on conventionally-farmed fields. In Spain, birds bred more often, and rare species bred and foraged more often in areas under a scheme designed to promote the conservation of steppe-associated birds than on paired sites without the scheme. In the Netherlands, more birds bred on 12.5 ha plots consisting of a mixture of fields with postponed agricultural activities and fields with a per-clutch payment scheme. However, the number of bird species on each type of farmland also did not differ between agri-environment schemes and non- agri-environment scheme plots, and there was no difference in bird abundance and breeding on those fields with only postponed agricultural activities compared with conventionally farmed fields. In Spain, the agri-environment scheme included limits on annual fertiliser and pesticide application; a month of restricted agricultural activity between April and July; mandatory unploughed strips covering three percent of fields; ploughing restrictions and a ban on burning fallow vegetation. In the Netherlands, the scheme prohibited changes in field drainage, pesticide application (except for patch-wise control of problem weeds) and any agricultural activity between 1 April and early June. Additionally, farmers of surrounding fields were paid for each meadow bird clutch laid on their land (though no agricultural restrictions were in place on these fields). In both countries, seven pairs of fields were surveyed in three parts of the country, four times over the breeding season.
A replicated study in 1999 and 2003 on 84 farms in East Anglia and the West Midlands, England (Stevens & Bradbury 2006), found that only three species (two in East Anglia, one in the West Midlands) showed a significant positive response to the introduction of agri-environment schemes, whilst one showed a significant negative effect. Meadow pipits Anthus pratensis, carrion crows Corvus corone and reed buntings either declined less or increased on farms under agri-environment schemes, compared to conventionally managed farms,. Corn buntings Miliaria calandra declined significantly faster on agri-environment scheme farms. Overall, only six species showed any positive response (significant or not) in both regions, ten showed negative responses in both and 12 showed a positive response in one region and a negative response in the other. The impacts of individual management options are discussed in the relevant interventions.
A single farm, Rawcliffe Bridge, East Yorkshire, UK (Bryson et al. 2007), with a combination of conservation measures prescribed under the English Entry Level Stewardship Scheme had higher densities of some bird species than the average for UK lowland farms. Meadow pipit, reed bunting, Eurasian skylark, grey partridge, corn bunting and yellow wagtail occurred in higher numbers in each monitoring year than the average lowland farm density (provided by the British Trust for Ornithology). For example, there were between 12 and 22 meadow pipit pairs/100 ha at Rawbridge, compared to a national average of <3. Birds on the farm were monitored five times each year from 2003 to 2005, by walking the field boundaries. The number of breeding pairs/ha was estimated from clusters of sightings.
A 2007 systematic review of 29 studies incorporating data for 15 farmland bird species in the UK (Roberts & Pullin 2007) found that there were significantly higher winter densities of farmland birds on fields under agri-environment schemes than on conventionally managed fields. Considering each scheme individually, there was greater winter densities of birds on fields within the Arable Stewardship Pilot Scheme, Countryside Stewardship Scheme, fields with set-aside, overwinter stubble, and wild bird cover than on conventionally farmed fields. Overall, eight species (53%) had significantly higher winter densities on agri-environment fields compared to conventional cropping (corn bunting, greenfinch, grey partridge, northern lapwing, linnet, rook, Eurasian skylark and song thrush Turdus philomelos) and no species were found to have higher densities on conventional agricultural fields compared to those fields entered under agri-environment scheme agreements. Although set-aside fields in summer had significantly higher densities of farmland birds, there was no difference between the number of birds on conventionally farmed fields and Arable Stewardship Pilot Schemes fields in summer. Six (35%; grey partridge, northern lapwing, woodpigeon, Eurasian skylark, rook and cirl bunting) of the 17 species for which summer data were available were found at significantly higher densities on agri-environment scheme fields compared with fields under conventional systems. The migratory yellow wagtail Motacilla flava was found at lower densities on scheme fields than on conventionally managed fields. In total 29 papers describing experiments conducted between 1985 and 2005 on a total of 12,653 fields (5,381 fields under agri-environment schemes and 7,272 fields farmed conventionally) were used for the meta-analysis. The meta-analysis included seven site comparison studies, five randomised control trials and 17 controlled trials.
A 2007 site comparison study of 677 plots covering 38,705 ha across southern England (Wilson et al. 2007) found that for three wader species, population trends were more favourable (increasing or declining less rapidly) in areas under the Environmentally Sensitive Areas scheme options aimed at enhancing habitat than in the less expensive Environmentally Sensitive Areas habitat maintenance options and in parts of the surrounding countryside not participating in the scheme. However, population trends were most favourable on nature reserves. Between 1982 and 2002, common redshank declined by 70% in the wider countryside but increased overall from 646 to 755 pairs (up 17%) on Environmentally Sensitive Areas designated land (compared with 160% increases on non-Environmentally Sensitive Areas reserves). Northern lapwing showed a 48% decline in the wider countryside, but increased in reserves with Environmentally Sensitive Areas enhancement by 121% (compared with a 55% increase in non-Environmentally Sensitive Areas reserves). Common snipe breeding numbers decreased everywhere, but declines were smaller in reserves in Environmentally Sensitive Areas (24% decline) compared with reserves outside Environmentally Sensitive Areas (66% decline) or the wider countryside (up to 90% declines). Breeding waders were surveyed in 1982 and 2002 at lowland wet grassland sites covering ten counties in England. In both years, three censuses were carried out at each site between mid-April and mid-June.
A before-and-after study, examining data from 1976-2003 from farms across southern Sweden (Wretenberg et al. 2007) found that four locally migrant farmland birds (northern lapwing, Eurasian skylark, common starling and linnet) showed less negative (or positive) population trends during 1987-1995, a period of agricultural extensification which included the introduction of agri-environment schemes, compared to in the preceding period of intensification (1976-1987). However, following the adoption of the Common Agricultural Policy in 1995-2003, the species showed more negative population trends again, despite the widespread adoption of agri-environment scheme options. Three non-migrant species (house sparrow Passer domesticus, tree sparrow P. montanus and yellowhammer Emberiza citrinella) showed more diverse population trends and responses to agricultural changes were largely non-significant.
A study of the locations of Meadow Bird Agreements in the Netherlands (Melman et al. 2008) found that 43% of the 71,982 ha of Meadow Bird Agreements area in 2004 was located on sites where meadow bird populatons are constrained for reasons other than those addressed by the agri-environment management. Twenty-two percent (15,798 ha) were outside the area of known black-tailed godwit Limosa limosa occurence (more than five breeding pairs/100 ha in a 1998-2000 survey; 90-95% of other specialist meadow bird species breed in suitable black-tailed godwit habitat). Within the black-tailed godwit area, 11% (6,166 ha) of the Meadow Bird Agreements area was on heavily drained land, 4% (2,500 ha) was in landscapes not considered open enough for meadow birds, 10% (5,400 ha) was in areas of high traffic disturbance and an estimated 8% (2,834 of the 35,000 ha for which data were available) was on sites with high predation. The authors advocated targetting Meadow Bird Agreementsto the 285,000 ha of land in the Netherlands with more than five breeding pairs of black-tailed godwit/100 ha, but none of the other identified constraints.
A replicated 2008 site comparison study of 53 2 km² plots on 14 farms in southeast Scotland (Perkins et al. 2008) observed that between 2002 and 2004, the number of territorial male corn buntings fell by only 5% on plots that managed land according to the Farmland Bird Lifeline scheme, whereas numbers declined by 43% in non- Farmland Bird Lifeline plots in the same area. Between 2000 and 2002, before the 2002 introduction of the Farmland Bird Lifeline management practices, there was no observed change in the number of corn buntings on either group of plots – although plots destined to participate in the Farmland Bird Lifeline scheme did already have 33% higher densities of corn bunting than comparison plots. The Farmland Bird Lifeline scheme intended to reverse the declining numbers of corn bunting, a priority species in the UK Biodiversity Action Plan. Farmers were paid for a number of interventions, including providing grass margins to arable fields, farming spring cereals and turnips at low intensity, spring cropping, leaving unharvested crop, and supplementary feeding. Fourteen farms, nine in Aberdeenshire and five in Fife, were surveyed every breeding season (late April to August) from 2000 to 2004.
A 2008 literature review of the Environmental Stewardship programme, particularly Entry Level Stewardship in the UK (Vickery 2t al. 2008) found that the amount of land entering the scheme was on target, but that several classes of options were not being taken up at a high enough rate to maintain some farmland birds. The authors argue that ‘in-field’ options such as skylark plots, conservation headlands and stubbles (all are discussed in their own sections) need to be promoted, as do complex field-edge options such as ‘enhanced hedgerow management’. The rate of Entry Level Stewardship uptake in 2008 was estaimted to be sufficient to promote population growth in only two of 12 species studied, and close in another. Even with a 70% uptake rate, the scheme was not predicted to promote population growth in five species (northern lapwing, European turtle dove Streptopelia turtur, yellow wagtail, Eurasian linnet and yellowhammer). The authors warn, however, that their analysis may have under estimated the effectiveness of Entry Level Stewardship.
A 2008 site comparison study of ten 3 km² plots in Austria (Wrbka et al. 2008) showed that, compared to conventionally managed arable land, land farmed less intensively (under agri-environment schemes) had larger numbers of ground breeding birds (16 vs. 13 individuals/10.ha), red listed birds (3 vs. 2 individuals/10 ha), and Species of European Conservation Concern (14 vs. 10 individuals/10 ha). Arable land managed for the conservation of particular species had 27 Species of European Conservation Concern individuals/10 ha and 29 ground breeding individuals/10 ha compared with the 11 and 14, respectively, on conventionally managed farmland. Reed-breeding birds on grassland benefited from similar initiatives (11 vs. 3 individuals/10 ha of farmland). Habitat conservation measures appeared to benefit ground breeders on arable farmland (17 vs. 10 individuals/10 ha). Breeding birds were surveyed during three visits between April and June 2003.
A 2009 literature review of agri-environment schemes in England (Natural England 2009) found that options and schemes varied in effectiveness. Breeding populations of some nationally rare birds increased after the implementation of options on arable farms (cirl bunting pairs increased by 130%, Eurasian thick-knee pairs by 87%) and a case study from a single farm found that grey partridge numbers increased by more than 250%/year; corn buntings by over 100%/year and Eurasian skylarks by 71%/year following the implementation of a number of different options. Productivity of some species was found to be higher on agri-environment scheme farms, which also provided key habitats. However, there was little evidence for any population-level beneficial effects of Entry Level Stewardship designation on widespread birds such as skylarks or yellowhammers E. citrinella. Several studies reviewed argued that most agri-environment scheme schemes were not well targeted to provide habitat for waders, although other studies argued that wader populations had declined less in regions designated as agri-environment schemes than in the country overall. The effects of individual options on birds are discussed in the relevant sections.
A replicated paired sites study on farms across Scotland under two agri-environment scheme prescriptions (Countryside Premium Scheme and Rural Stewardship Scheme) in spring-summer 2004-2008 (Parish et al. 2009) concluded that the schemes had little impact on farmland biodiversity. Whilst 280 agri-environment scheme farms had more birds of more species than 193 non-scheme paired farms (averages of 140 birds of 23 species on 105 Countryside Premium Scheme farms vs. 108 of 20 on paired non-scheme farms; 108 birds of 19 species on 88 Rural Stewardship Scheme farms vs. 86 of 17 on paired farms), trends did not vary between scheme and non-scheme farms, and scheme farms had higher species richness and abundances before entering schemes. Differences held for all species and for nationally threatened species. Time since entry into the Countryside Premium Scheme did not appear to affect the number of species or bird abundance, except for a small decline in the abundance of tits Parus spp. In addition, no evidence was found for differing effects of schemes in different regions of Scotland, or on different farm types.
A controlled study in 2002-9 on mixed farmland in Hertfordshire, England (Aebischer & Ewald 2010), found that the estimated population density of grey partridges was significantly higher on land under agri-environment schemes than on conventional arable crops. This study also examined the densities found on set-aside (which were similar to those on land under other agri-environment schemes, see ‘Provide or retain set-aside’), wild bird cover (which were considerably higher than on other land uses, see ‘Plant wild bird seed or cover mixture’) and the impact of predator control and supplementary food provision (see ‘Provide supplementary food to increase adult survival’ and ‘Control predators not on islands’).
A large 2010 site comparison study of 2,046, 1 km² plots of lowland farmland in England (Davey et al. 2010) found that the Countryside Stewardship Scheme and Entry Level Stewardship schemes had no consistent effect on farmland bird numbers three years after their introduction in 2005. Between 2005 and 2008 eight Farmland Bird Index species showed significant declines on arable plots, nine species declined significantly on pastoral plots and six species declined on mixed farmland squares (farmland plots covered with less than 50% arable and less than 50% pastoral farming). Only goldfinch Carduelis carduelis, jackdaw Corvus mondedula and woodpigeon showed population increases between 2005 and 2008. Although certain farmland bird species did show landscape-specific effects, there were no consistent relationships between farmland bird numbers and whether or not the plots contained Entry Level Stewardship and Countryside Stewardship Scheme land, or the financial cost of the agri-environment interventions, or the length of hedgerows or ditches under an agri-environment scheme, or the availability of wild bird seed mix and over-winter stubbles (i.e. some species showed increases in response to a particular intervention on a particular landscape-type but not on other landscape-types, and these changes were not consistent between species). The 2,046 1 km² lowland plots were surveyed in both 2005 and 2008 and classified as arable, pastoral or mixed farmland. Eighty-four percent of plots included some area managed according to the Entry Level Stewardship or Countryside Stewardship Scheme. In both survey years, two surveys were conducted along a 2 km pre-selected transect route through each 1km² square.
A replicated site comparison of the same 2,046, 1 km squares of agricultural land across England as in (27) in April-June 2005 and 2008 (Davey et al. 2010) found that farmland bird population responses to Entry Level Stewardship schemes varied regionally. The authors suggest that detailed, regional prescriptions may be more effective in stimulating population growth than uniform agri-environment schemes. Field margin management took place in 36% of squares and did not have clear impacts on ‘field margin’ species: two responded positively in at least one region, three species showed positive and negative responses in different regions, one only negative responses and the other six showed no significant responses.
A replicated site comparison study on 1,031 agricultural sites across England in 2004-2008 (Ewald et al. 2010) found that in three out of four year-on-year comparisons, grey partridge Perdix perdix density changes and overwinter survival were higher on sites under agri-environment schemes, than on sites not under schemes (density changes were more positive on agri-environment scheme sites than non-agri-environment scheme sites in all comparisons except 2007-2008; overwinter survival was higher for all except 2006-2007). However, these differences were only significant in 2005-6 for density changes (6% increase on agri-environment scheme sites vs. 11% decrease on non-agri-environment schemes sites) and 2006-2007 for overwinter survival. There were no consistent differences between agri-environment schemes and non-agri-environment scheme sites with respect to brood size. When schemes were investigated individually, only Countryside Stewardship Scheme sites and Environmentally Sensitive Areas sites had significantly more positive density trends than non-scheme sites, and only in 2005-2006 (6% increase on Countryside Stewardship Scheme and Environmentally Sensitive Areas sites vs. 12% decline on non-agri-environment scheme sites), although other years and schemes showed a similar pattern. Overwinter survival, brood size and the ratio of chicks to adults did not show consistent effects across different schemes. These individual options are discussed in the relevant sections. Various methods of succession management (rough grazing, scrub creation, scrub control, grassland creation) were negatively associated with the ratio of young to old partridges in 2008.
A small 2010 site comparison study of 75 fields in East Anglia and the West Midlands, UK, (Field et al. 2010) found no difference between the numbers of seed-eating birds in fields managed under the Higher Level of the Environmental Stewardship scheme and numbers in fields managed under the Entry Level of the scheme. Entry Level Stewardship fields had stubbles and were prohibited from post-harvest herbicide and cultivation until mid-February, and were planted overwinter with wild bird seed mix. Higher Level Environmental Stewardship fields were planted with enhanced wild bird seed mix and the stubbles had the basic Entry Level Stewardship requirements plus reduced herbicide use. These interventions are discussed in more detail in ‘Plant wild bird seed or cover mixture’ and ‘Leave overwinter stubbles’.
A 2010 before-and-after trial of the Entry Level Stewardship on a 1,000 ha lowland arable farm in central England (Hinsley et al. 2010) observed that the number of seed-eating birds was higher on both Entry Level Stewardship and conventionally farmed fields in the winter of 2006/2007 than during the previous winter – when the Entry Level Stewardship was first introduced. This increase was greater on Entry Level Stewardship plots setting aside five percent of farmland to provide winter bird food (with an average of 70 birds/km of transect in 2007 vs. 5 birds/km of transect in 2006) than on conventionally farmed fields (25 birds/km of transect in 2007 vs. 10 birds/km of transect in 2006). Although there were also more summer breeding territories of seed-eating species, chaffinch Fringilla coelebs, dunnock Prunella modularis, and robin Erithacus rubecula on the farm as a whole in 2007 than in the previous breeding season, there was no difference in this increase between Entry Level Stewardship and conventional fields. Land managed according to the minimal environmental requirements was compared both with fields where five percent of land was removed from production and replaced with patches of winter bird food and field margins (6–8 m). Winter birds were surveyed from transects on three visits (November, December, and January) in both the winters of 2005/2006 and 2006?2007 - i.e. before and after bird food patch establishment. Breeding territories were surveyed during four visits (April, May, June, and July) in 2006 and 2007.
- Ovenden G., Swash A. & Smallshire D. (1998) Agri-environment schemes and their contribution to the conservation of biodiversity in England. Journal of Applied Ecology, 35, 955-960
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