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ORIGINAL PAPER

Effects of agri-environment managementfor cirl buntings on other biodiversity

Michael A. MacDonald • Gail Cobbold • Fiona Mathews •

Matthew J. H. Denny • Leila K. Walker • Philip V. Grice •

Guy Q. A. Anderson

Received: 15 August 2011 /Accepted: 14 February 2012! Springer Science+Business Media B.V. 2012

Abstract Agri-environment scheme (AES) management has increased populations of cirlbuntings (Emberiza cirlus) in South Devon, England, and might be expected to providebenefits for other declining biodiversity, due to less intensive farm management. Fieldsmanaged under AES for cirl buntings (low-input spring barley or permanent pasturewithout inputs) were contrasted with control fields under conventional management (springbarley without management restrictions and winter cereals, or grazed without managementrestrictions) to identify such benefits for vascular plants, butterflies, bumblebees, carabidbeetles, foliar invertebrates and bats. Activity-density and species richness of carabidbeetles were both higher in AES spring barley fields than in control spring barley andwinter cereal fields. Forb cover and abundance of butterflies and bumblebees were higherin AES spring barley fields than in winter cereals, but did not differ between AES and

M. A. MacDonald ! G. Cobbold ! L. K. Walker ! G. Q. A. AndersonRSPB, The Lodge, Sandy SG19 2DL, UK

Present Address:M. A. MacDonald (&)RSPB Cymru, Sutherland House, Cowbridge Road East, Cardiff CF11 9AB, UKe-mail: michael.macdonald@rspb.org.uk

Present Address:G. CobboldAdonis Ecology Limited, Unit 11 Lavenham Studios, Brent Eleigh Road, Lavenham CO10 9PE, UK

F. MathewsHatherly Laboratories, University of Exeter, Prince of Wales Road, Exeter EX4 4PS, UK

M. J. H. DennyDenny Ecology, 17D Sturton Street, Cambridge CB1 3BY, UK

Present Address:L. K. WalkerDepartment of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK

P. V. GriceNatural England, Floor 3, Touthill Close, City Road, Peterborough PE1 1UA, UK

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control spring barley. No difference was observed in plant species richness between any ofthe arable field types. Plant species richness and butterfly abundance were higher in AESpasture fields than in controls. Abundance, activity-density and/or species richness of othertaxa did not differ between AES and control pastures. Benefits observed in AES springbarley fields arise from management specific to AES agreements, and also, we suggest,from the maintenance of spring-sown barley in the landscape. Benefits in AES pasturefields are ascribed to the absence of fertiliser and pesticide inputs, and reductions instocking arising from this; there is also likely to have been some pre-selection for olderpastures to be entered into AES management agreements. Agri-environment measures forcirl buntings have benefits for a range of taxa beyond the target species, and therefore,largely through reduction of management intensity and maintenance of land-use diversity,improve the overall biodiversity of the farmed landscape where they are present.

Keywords Agri-environment scheme ! Bats ! Bumblebees ! Butterflies ! Carabid beetles !Cirl bunting ! Plant species richness reduced input farming ! Spring barley

Introduction

In the second half of the twentieth century, agricultural intensification pushed the cirlbunting (Emberiza cirlus) to the brink of extinction in the UK, with only a small populationof around 120 pairs persisting in south Devon (Evans 1997). Autecological research intothe biology of cirl buntings helped to diagnose the proximate causes of the populationdecline (Evans and Smith 1994; Evans et al. 1997). These were: the loss of winter food dueto the shift from spring- to winter-sown crops and the consequent loss of weedy over-wintered stubbles; the general loss of arable cropping in grass-dominated landscapes; theloss of large insect food for chicks in the breeding season, due to the intensification ofgrassland management; and the loss of suitable nest sites due to the removal of hedges andunsympathetic management of those that remained.

Agri-environment schemes (AES) are the major tool used by European Union memberstates to attempt to address the loss of biodiversity from agricultural landscapes (Kleijn andSutherland 2003). In 1993, a ‘‘special project’’ option within the English CountrysideStewardship Scheme (CSS) was created to address what were considered to be the primarycause of cirl bunting decline (Jeffs and Evans 2004). The special project involved theprovision of weedy overwinter stubbles following low-input spring barley crops, whichwas offered as part of a package of AES measures designed to meet the year-roundrequirements of the birds (including the provision of extensively-managed grassland andgrass margins, and the creation and maintenance of high quality hedgerows). Uptake of thespecial project proved popular—by 1999, 120 CSS agreements had created 300 ha ofweedy overwinter stubbles—and a marked increase in cirl bunting breeding densitiesoccurred in areas with targeted CSS agreements (Peach et al. 2001). By 2004, over1,000 ha of special project stubbles and 1,700 ha of extensively-managed grassland hadbeen put in place under CSS (Jeffs and Evans 2004), and the most recent cirl buntingpopulation estimate was 862 pairs in 2009 (Stanbury et al. 2010; Davies et al. 2011).

Despite the success of the special project in increasing cirl bunting numbers, there havebeen criticisms of the single-species approach to AES (Kleijn and Sutherland 2003;Berendse et al. 2004; Kleijn et al. 2006). Specifically, questions have been raised about thecost and effort involved in AES for single species, and whether habitat improvementsaimed at a target species can provide general benefits to farmland biodiversity. However,

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the AES stubbles created for cirl buntings have already had demonstrable benefits for othergranivorous birds, many of which are in decline and, hence, of high conservation concern(Bradbury et al. 2008), while plants of conservation interest have been recorded on sitesmanaged for cirl buntings (Lock 1999).

The aim of the present study was to test whether cirl bunting AES management pro-vided benefits at the field-scale for vascular plants, carabid beetles, foliar invertebrates,butterflies, bumblebees and bats. These groups were selected after discussion with expertsin a wider range of taxa, because they were considered likely to respond to AES man-agement, were likely to be recorded in sufficient numbers to demonstrate such responses,and because they would allow for a survey programme that could be conducted in a singleyear. The null hypothesis was that there would be no difference in the abundance (but-terflies, bumblebees, foliar invertebrates), activity-density (carabid beetles), cover (forbs),species richness (vascular plants and carabid beetles), or activity (bats) between fieldsunder AES management and control fields.

Two whole-field prescriptions implemented to benefit cirl buntings (Jeffs and Evans2004) were surveyed:

(1) AES spring barley, managed with reduced pesticide inputs where the field is left post-harvest as a stubble until the following April; and

(2) AES pasture managed with no pesticide or fertiliser inputs

Other prescriptions available for cirl buntings, notably grass margins and hedgerowmanagement, were not surveyed. This was partly because the benefits of equivalentmeasures have been tested elsewhere (e.g. Critchley et al. 2006; Pywell et al. 2006; Merckxand Berwaerts 2010), and partly because we were interested in the performance of AESoptions beyond boundary features.

Methods

Study area

We selected sites in the core cirl bunting population area of south Devon, England, whichstretches from approximately 50.3"N 4.1"W to 50.7"N 3.5"W. Both AES spring barley andAES pastures were available under CSS until this scheme ended for new entrants in 2004,and there are now equivalent or similar prescriptions in Environmental Stewardship,particularly within Higher Level Stewardship (see http://www.naturalengland.org.uk/ourwork/farming/funding/es/default.aspx). However, at the time when field work wasundertaken, most AES land was still under CSS agreements that had not reached the end oftheir ten-year term.

Matched control fields were selected that were not under AES management but wereotherwise as similar as possible to the AES fields (based on topography, size andlandscape context), and which could conceivably have been under such management.Where possible these were on the same farm, but in some cases they were on adjacentproperties. Distance of control fields from AES fields ranged from 0 to 3,700 m (med-ian = 175 m; only 5 control fields[1 km distant). For AES pasture, the control fieldswere pastures without management restrictions. For AES spring barley, there were twopossible controls: conventional spring barley, and winter cereal (barley or wheat), both ofwhich were free from management restrictions. All control fields were able to receivehigh levels of fertilisers and pesticides, and to be heavily stocked in the case of control

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pastures. However, this did not necessarily happen, as the intention was to determine thecounterfactual, or what would have been present in the absence of AES, and this couldalso have included low intensity farming. Survey sites were selected at random from theavailable farms in AES agreements targeted at cirl buntings and included 25 AES pasturefields and 22 AES spring barley fields, on 32 farms. Eleven AES spring barley sites werematched with both controls, eight with winter cereal only, and three with conventionalspring barley only (a total of 33 control fields). The paired AES and control fields aredescribed as a site in analyses.

Field surveys

Plants were surveyed between 30 June and 5 August 2008. Ten 0.5 9 0.5 m quadratswere placed equidistantly along a transect parallel to the longest axis of the field. Vas-cular plants were identified to species wherever possible, otherwise to genus, and totalplant species richness was the response variable. Cover was recorded on a modifiedBraun-Blanquet scale (categories being:\1%, 1–5%, 5–25%, 25–50%, 50–75%,75–100%). Total forb cover was not recorded during the surveys, but was estimatedafterwards from the data sheets using the modified Braun-Blanquet scale and used as aresponse variable.

Butterflies and bumblebees were surveyed three times in arable fields and four times ingrass fields. Periods for survey rounds were 6–29 May, 9 June-8 July, 10 July-12 August,and 27 August-19 September (grass fields only in final round). Transects were walkedalong the long axis of each field and all bumblebees and butterflies within 2.5 m wererecorded and identified to species where possible (Bombus terrestris and B. lucorum wererecorded as a single species in all cases), following methods described by Pollard andYates (1993). Transects ranged from 112 to 460 m (median = 221 m) in arable fields, and72 to 358 m (median = 168.5 m) on pasture fields. The response variable was the max-imum count of all butterflies or bumblebees.

Pitfall traps of 8 cm diameter were placed at locations 20, 50, and 100 m distant fromfield boundaries; in some small fields, pitfall traps could not be placed 100 m distant froma field boundary, and in these cases they were placed as distant from the field boundary aspossible. Traps were filled with a mixture of propylene glycol and water, with a pinch ofcayenne pepper added to deter animals likely to remove traps. Traps were covered withwire mesh (12.5 mm diameter) held in place with wire staples, to reduce by-catch of smallmammals and loss of traps to animals. Traps were left open for 1 week, with starting datesranging from 16 June to 4 July in arable fields, and from 25 August to 5 September in grassfields. One pasture site was not sampled, and there were some losses to animals. Only trapsfrom field locations where they remained intact in both AES and control fields wereincluded in analyses. The sampling period was relatively short, but data from shorterperiods are still of value, as they report the approximate rank and relative proportions ofthe dominant species (Niemela et al. 1986). Carabid beetles were identified to species (Luff2007), with a very small number of exceptions, which were identified to genus. Activity-density (number of individuals caught) and species richness per trap were used as responsevariables. In grass fields, sward height was measured at ten random points along butterfly/bumblebee transects: this was done on the day of butterfly/bumblebee transects, which wasusually the day of putting in or taking out pitfalls, but occasionally could be up to a weekbeforehand or afterwards.

Foliar invertebrates were collected from pasture fields at 13 sites, on dates ranging from10 June to 4 July. Starting 20 m from the field boundary, 80 sweeps of the net were made at

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a steady pace walking towards the centre of the field. Invertebrates were identified tofamily, and abundance of each family was used as a response variable. Sward height wasmeasured at ten random points along the transects on the same day as the sweep netsamples were taken, and the average of these measurements was used both as a responsevariable (to test whether it differed between AES and control pastures), and as a predictorvariable (to test whether it had an independent effect on the abundance of foliar inverte-brates) as described in the data analysis section.

Bat activity was surveyed at grass sites using static Anabat (Titley Electronics, Bal-lina, Australia) detectors that were left out overnight in AES and control pasture fields onthe same night. Bat echo-location calls are recorded and retrieved from a memory cardafter the event. Bats were identified to species except for species in the genera Myotisand Nyctalis, which are often not reliably distinguished. Due to the low number of callsrecorded, total number of bat passes (defined as at least two calls separated by less thanone second; Walsh and Harris 1996) was the response variable. Detectors were placedtwenty metres in from the field boundary, facing the centre of the field and in such a wayas not to be facing adjacent woods or drainage lines. Eighteen sites were surveyed intotal. Nine sites were surveyed from 12 May to 29 May: seven of these were re-surveyedlater in the year (15 July to 10 August), during which period a further nine sites weresurveyed.

Data analysis

The effects of AES agreement status on the response variables were modelled usingGeneralized Linear Mixed Models. In arable fields, separate analyses were conductedbetween AES spring barley and conventional spring barley and winter cereals respec-tively. Agri-environment status was included as a fixed effect in all models, and site(paired AES and control fields) was included as a random effect in all models. For batactivity, a visit term was included as a fixed effect, and field (nested within site) wasincluded as an additional random effect, to account for multiple surveys at some sites.For pitfall trap data, field (nested within site) was included as an additional randomeffect, to account for multiple samples from fields. The location of the pitfall trap inrelation to the field edge was included as a categorical fixed effect, as was an interactionterm between trap location and AES status. These interactions were removed frommodels if they proved to be non-significant. For sweep sample data and pitfall trap datain pasture fields, sward height was modelled as a response variable between AES andcontrol pastures, and was also included as a continuous fixed effect in models of theabundance of foliar invertebrates.

Models were implemented using PROC GLIMMIX of the SAS (v. 9.1) statisticalpackage (Littell et al. 1996). Plant species richness, logit-transformed forb cover, andsward height were modelled using a normal error structure and an identity link function.Bat activity and carabid species richness were modelled using a negative binomial errorstructure and a log link function. Butterfly, bumblebee foliar invertebrate abundances, andcarabid activity-density were modelled using a Poisson error distribution, log link function,with survey area as an offset for butterflies and bumblebees. A scaling parameter (the‘‘random_residual_’’ option in SAS) was also included in the models of foliar inverte-brates, of carabid activity-density, and of bumblebees on pasture fields, to account foroverdispersion of the data. Values presented are back-transformed means and standarderrors, which may be asymmetrical. F-values are presented with numerator and denomi-nator degrees of freedom as sub-scripts.

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Results

Plants

Plant species richness was significantly higher on AES pastures than on control pastures(F1,24 = 17.76, p = 0.0003), with the former averaging 6.4 more species, but there was noeffect on percentage forb cover (F1,24 = 0.02, p = 0.90; Fig. 1).

There was no significant difference in plant species richness between AES spring barleyand conventional spring barley (F1,12 = 0.01, p = 0.9056) or winter cereals (F1,18 = 2.45,p = 0.1346; Fig. 2). Percentage forb cover was significantly higher in AES spring barleythan winter cereals (F1,18 = 15.55, p = 0.001), though not than conventional spring barley(F1,12 = 0.52, p = 0.4829; Fig. 2).

Bats

Seven bat taxa were recorded, which were: common pipistrelle Pipstrellus pipistrellus(recorded at eight AES and five control sites); soprano pipistrelle P. pygmaeus (two AESand two control); Nyctalis sp. (six AES and two control); Myotis sp. (four AES and onecontrol); greater horseshoe bat Rhinolophus ferrumequinum (one AES and one control);long-eared bat Plecotus auritus (three AES and one control); and serotine Eptesicusserotinus (three AES and one control). Over two-thirds of passes recorded were of commonpipistrelles. There was no significant effect of AES status on bat activity, although therewas a trend towards recording more passes over AES pastures (AES pas-ture = 3.19 ? 1.57/-1.05 passes/night, control pasture = 1.23 ? 0.68/-0.44 passes/night; F1,13 = 2.57, p = 0.1329). There was an effect of survey period, with significantlymore calls being recorded in the earlier surveys (F1,13 = 16.50, p = 0.0013).

Fig. 1 Plant species richness (filled columns) and back-transformed % forb cover (open columns) on AESand control pastures. SE bars presented

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Butterflies and bumblebees

There was a significant effect of AES status in arable fields for both butterflies andbumblebees (Fig. 3). Maximum abundance was higher in AES spring barley field typesthan in winter cereals (bumblebees: F1,18 = 19.61, p = 0.0003; butterflies: F1,18 = 10.24,p = 0.005). Abundances of bumblebees and butterflies were respectively 27 and 10 timesas great in AES spring barley than in winter cereals. Abundance of neither group differedbetween AES and conventional spring barley; in fact, bumblebee abundance was mar-ginally higher in conventional spring barley fields (bumblebees: F1,13 = 4.09, p = 0.0643;butterflies: F1,13 = 0.27, p = 0.6107).

In pasture fields, there was an effect of AES status on maximum butterfly abundance(Fig. 4), which was five times higher on AES pastures than control pastures

Fig. 2 Plant species richness (filled columns) and back-transformed % forb cover (open columns) on AESspring barley and control fields. SE bars presented

Fig. 3 Maximum abundance per hectare (back-transformed) of butterflies (open columns) and bumblebees(per hectare) in AES spring barley and control fields. SE bars presented

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(F1,24 = 39.37, p\ 0.0001). There was no difference in the maximum abundance ofbumblebees between AES and control pasture fields (F1,24 = 0.07, p = 0.7921; Fig. 4).

Foliar invertebrates

There was no effect of AES status on the abundance of any of the groups tested (Spiders:F1,11 = 0.26, p = 0.6171; adult Diptera: F1,11 = 0.12, p = 0.7354; Hymenoptera:F1, 11 = 0.24, p = 0.6316; Heteroptera: F1,11 = 0, p = 0.9629; Fig. 5). Average canopyheight and the coefficient of variation in canopy height did not differ significantly betweenAES and control pastures (AES pasture mean = 16.6 ± 2.4 cm, control pasturemean = 15.3 ± 2.4 cm; F1,12 = 0.17, p = 0.6891). There was a trend for abundance ofall foliar invertebrates to increase with sward height, which was non-significant for spiders(estimate = 0.0191 ± 0.0159; F1,11 = 1.44, p = 0.2551), marginally significant for adultDiptera (estimate = 0.0378 ± 0.0194; F1,11 = 3.79, p = 0.0775) and for Hymenoptera(estimate = 0.0361 ± 0.0167; F1,11 = 4.66, p = 0.0538), and significant for Heteroptera(estimate = 0.1034 ± 0.0412; F1,11 = 6.29, p = 0.0291).

Carabid beetles

Losses to animals meant that no paired pitfall traps remained in place at one pasture site;paired traps were available for the location nearest the edge of the field at 18 sites, theintermediate location at 22 sites, and the location furthest from the field edge at only threesites (the reason for this greater loss of traps is unknown). In pasture fields, therefore, traplocation was a two-category variable, with intermediate and central field trap locationscombined as a single category. In the pasture fields, there was no main effect of AES statuson activity-density (AES mean = 3.80 ? 0.90/-0.73, control mean = 3.90 ? 0.92/-0.74; F1,37 = 0.01, p = 0.9202) or species richness (AES mean = 1.83 ? 0.23/-0.21,Control mean = 2.02 ? 0.25/-0.22; F1,37 = 0.38, p = 0.5389). There was a marginaleffect of trap location on abundance (F1,37 = 3.16, p = 0.0839), with fewer caught in trapsat the field edge, but no effect on species richness (F1,37 = 0.20, p = 0.6555), and the

Fig. 4 Maximum abundance per hectare (back-transformed) of butterflies (open columns) and bumblebees(per hectare) in AES and control pasture fields. SE bars presented

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non-significant interactions were not included in the final models. There was no effect ofsward height on activity-density or species richness (activity-density: F1,37 = 0.23,p = 0.6351; species richness: F1,37 = 0.64, p = 0.4278), and sward height did not differbetween AES and control pasture fields (F1,21 = 0.013, p = 0.723).

In the AES spring barley comparison with winter cereals, trap pairs remained in place atten, sixteen and fourteen sites respectively for the locations nearest to furthest from thefield edge. In the AES spring barley comparison with control spring barley, these figureswere ten, thirteen and nine sites. Carabid activity-density and species richness were sig-nificantly higher in AES spring barley fields than in control spring barley (activity-density:F1,34 = 15.74, p = 0.0004; species richness: F1,36 = 7.36, p = 0.0102) and wintercereals, marginally so in the case of activity-density (activity-density: F1,44 = 3.90,p = 0.0546; species richness: F1,44 = 5.02, p = 0.0302; Fig. 6). There was a significant

Fig. 5 Mean number of foliar invertebrate groups per sweep net sample (back-transformed) on grass fields.SE bars presented

Fig. 6 Mean back-transformed activity-density (filled columns) and species richness (open columns) perpitfall trap of carabid beetles on AES spring barley, control spring barley, and winter cereal and controlpasture fields. SE bars presented

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interaction between trap location and AES status in the comparison with control springbarley for activity-density (F2,34 = 3.49, p = 0.0419), with fewer carabids caught incentral field traps in control fields. There was no significant interaction for any of the othercomparisons, and these interaction terms were removed from the models. There was a maineffect of trap location on activity-density in the comparison with winter cereals, with fewercarabids caught in traps at the field edge (F2,44 = 6.46, p = 0.0035). There was no maineffect of trap location on species richness in either comparison (control spring barley:F1,36 = 1.86, p = 0.1704; winter cereal: F2,44 = 0.37, p = 0.6941).

Discussion

Vascular plants

Several of the groups that were surveyed showed benefits from AES management targetedat cirl buntings. As AES spring barley was introduced to provide winter seed food for cirlbuntings, higher forb cover in summer is a natural result of AES management (althoughcontrol spring barley had equivalent forb cover). Increased plant species richness is not agoal in itself, as long as seeds are produced, but it might have been expected. Previousstudies have found that plant species richness is higher in conservation headlands (i.e.where the outer edge of the crop does not receive any pesticides and, in some cases,fertiliser) (Chiverton and Sotherton 1991; de Snoo 1997; Kleijn and van der Voort 1997;Pywell et al. 2007; Walker et al. 2007). As there are restrictions on the pesticide load onAES spring barley, one might expect that such fields might act as whole-field conservationheadlands. In fact, there is some evidence that this occurs for invertebrate groups, asdiscussed below. One explanation might be that pesticide and fertiliser inputs are con-sistently low across the board on farms with AES agreements, either because farmersmanaging their land in such a manner are more likely to enter AES, or because being inAES has altered farmers’ behaviour across their whole farms. However, using reportednitrogen inputs on winter wheat fields as an indicator of overall inputs suggests that this isunlikely to be the case. These typically ranged from 125 to 175 kg/ha, which is slightly lowcompared with 178 kg/ha for all England and Wales in 2008 (British Survey of FertiliserPractice 2011); however, as the south-west has the lowest rates of nitrogen application ontillage (undifferentiated by crop type) of any of the English regions in the survey, thesefarms are likely to be quite typical of the area. As AES fields can rotate around the farm,and may have followed a variety of crops, it may be that the benefits of reduced inputs onplant species richness are limited when the field receives conventional management inpreceding years, and the long term impoverishment of the seed bank may mean arableplants are not able to respond quickly to AES management.

The differences in plant species richness observed between AES and control pasturefields are consistent with studies of grass fields under different management intensity(Mountford et al. 1993; Kirkham et al. 1996; Fenner and Palmer 1998; Janssens et al. 1998;Critchley et al. 2002; Tallowin et al. 2005). It could be argued that differences observedbetween AES and control fields could be due to inherent characteristics (such as pastureage or floristic richness) of fields that were entered into AES agreements. Pasture age diddiffer significantly between treatments; mean (±SE) time since re-seeding for AES pasturewas 39.4 ± 3.6 years, and for control pastures was 21.5 ± 3.7 years (we assigned a valueof 50 years where the farmer could not recall when it had been last ploughed). However,

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without AES agreements, pastures may have been under similar re-seeding regimes to thecontrol fields, such that time since re-seeding might be considered a treatment effect.

Contemporary management (fertiliser and pesticide input, and stocking rates) alsodiffered between controls and AES pasture, but by less than might have been expected.Using nitrogen application as an indicator of inputs, AES fields received none, but themean (±SE) input on control pasture fields (of 20 sites where farmers provided infor-mation) was only 33.9 ± 11.0 kg/ha. Eleven of these received no nitrogen, and only onereceived more than 100 kg/ha. This is considerably less than the average of 100 kg/harecorded in south west England in the 1980s on non-dairy livestock farms (Hopkins et al.1985). The differences in plant species richness observed may indicate that only a smallreduction in fertiliser application may have a notable effect. More likely, it might suggestthat even low levels of fertiliser application are likely to have a depressing effect on plantspecies richness. There was also anecdotal evidence from farmers that they had reducedinputs in recent years to rely on residual fertility, so differences in soil fertility may notreflect inputs in 2008.

These agri-environment agreements do not include grazing prescriptions, but there wasa slight tendency to reduced grazing intensity, presumably because of the lower produc-tivity of AES pastures. Seventeen farmers provided information on whether stocking ratediffered between AES and control pastures, and twelve of these provided figures. Stockrate was higher on controls than on AES pastures at 8 out of 17 sites. The mean differencein livestock units was marginally significant (0.67 ± 0.16 se on AES pasture against1.06 ± 0.16 se on controls; t-stat = -2.02, p = 0.07, n = 12). Differences in plant spe-cies richness between the treatments appear to be driven by the different management ofthe fields, some of which is a direct result of AES (no fertiliser or pesticide inputs), some ofwhich is an indirect result (lower stocking rates), and some of which is partly a resultof AES, but may also be affected by inherent characteristics of fields (age of pasture: AESfields cannot be ploughed, but older pastures may have been chosen for agreements).

Butterflies and bumblebees

The results relating abundance of nectarivorous insects to AES, habitat and managementvariables are of interest, and generally consistent with what might be expected from agri-environment schemes. Both butterflies and bumblebees were more abundant in AES andcontrol spring barley than in winter cereals, which probably relates to the higher forb coverproviding more foraging opportunities. Butterflies have been recorded as being moreabundant in conservation headlands than control crop headlands (Dover et al. 1990;de Snoo et al. 1998), as have bumblebees in studies that have compared crops with a rangeof agri-environment options available in England (Pywell et al. 2005; Pywell et al. 2006;Carvell et al. 2007). Bumblebee abundances in spring barley crops in the present study arebroadly comparable with those from conservation headlands in these other studies (thoughdirect comparisons are not simple due to weather and location issues), which in turn areconsiderably lower than those in other agri-environment options surveyed in those studies.Differences were not noted between AES and control spring barley fields, so the value ofAES rather than crop type can legitimately be questioned, and this point is discussedfurther below.

Butterflies and bumblebees showed different responses to AES in grass fields, and thesedifferences make ecological sense. Butterflies appear to be responding to the higher plantspecies richness and forb cover on AES pastures. Negative effects on butterfly biodiversityhave been observed on grasslands elsewhere in Europe as a result of nitrogen application

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(Ockinger et al. 2006), and higher grazing intensity (Kruess and Tscharntke 2002b), in thelatter case without significant differences in vegetation height or plant species richness.Bumblebees did not show an effect of AES status, which suggests that the AES pasturesare not producing large numbers of flowering resources, which again is consistent withstudies of AES pastures and meadows elsewhere in Europe (Kohler et al. 2007). Thefindings of the present study concur with an experimental study of grassland managementfor nectarivorous insects (co-incidentally also in Devon, England, and contemporaneouswith this study). That study found that bumblebees were most abundant in sown optionsand virtually absent from grass fields, and that butterfly abundance was higher on moreextensively managed grasslands (Potts et al. 2009).

Bats

Greater bat activity might have been expected due to greater abundance of invertebrates onAES pastures, as has been observed on organically managed farms in southern Englandand Wales (Wickramasinghe et al. 2003; Wickramasinghe et al. 2004). However, theresults of the present study concur with those of a study of Scottish AES options (includingcreation and management of species-rich grassland), which found no effect on bat activity(Fuentes-Montemayor et al. 2011).

Foliar invertebrates

Agri-environment pasture management is intended to provide large-bodied insect food forcirl bunting chicks. Therefore, foliar invertebrates might have been expected to be moreabundant on AES pastures, although the groups that were sampled in this study are notnecessarily those of greatest importance in chick diets. In fact, abundances of these groups didnot differ between AES and control pastures. Reductions in species richness and/or abun-dance, and changes in species composition, have been observed in these groups in moreintensively managed grassland (Siepel 1990; Gibson et al. 1992; Kruess and Tscharntke2002a; Ryder et al. 2005; Zurbrugg and Frank 2006). However, such differences as there arebetween AES and control pasture management have not altered sward height between them,which is likely to be the strongest determinant of abundance of these groups. In fact, therewasat least a marginal positive effect of sward height on three of the four groups, independent ofAES status. This effect was not observed for spiders, a group that has been shown to besensitive to grassland management in fields and margins, particularly as it relates to swardstructure (Gibson et al. 1992; Baines et al. 1998;Morris 2000; Bell et al. 2001).We are unableto comment on species richness or composition of these groups in the present study. The onegroup of ground invertebrates that were identified to species, carabid beetles, showed nodifferences in either abundance or species richness between the AES and control pastures.Both of these measures have shown strong responses to grassland management in otherstudies (Morris and Rispin 1987; Haysom et al. 2004; Woodcock et al. 2007a; Woodcocket al. 2007b). Once again, the similarity in sward height between AES and control pasturessuggests that AES management does not create different habitat for this group.

Carabid beetles

In arable fields, carabid beetle activity-density and species richness were both higher inAES spring barley than in both control fields, in contrast to the response for plants and

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nectarivorous insects, where crop type appears to be most important. Higher activity-density and species richness of carabid beetles within AES spring barley have beenreported in conservation headlands, although in fact there is more commonly no difference(Frampton and Dorne 2007). Therefore, we may not have expected to find an effect in thepresent study, especially as other groups displayed no difference, at least between thespring barley fields. However, declines in activity-density of some species in arable fieldshave been ascribed to pesticide application (Kromp 1999). The results of the present studysuggest that the differences in permitted inputs between the AES and control crops aresufficient to make a difference to this group, though they are not for others. This is also thecase for the target bird species, as cirl buntings prefer to forage in winter stubbles fol-lowing AES rather than control spring barley (Bradbury et al. 2008).

Conclusion

The present study has concentrated on field-scale differences, with results that indicate thatboth arable and pastoral AES management provide benefits for biodiversity beyond pop-ulation increases for cirl buntings. It is reasonable to question whether these field-scaledifferences in counts or foraging activity translate into population-level effects on thesurveyed species. Proving population-level effects on groups such as bumblebees and batswould require much more intensive field surveys and censusing than were possible withinthe present study. However, given the lack of evidence for population benefits of targetspecies of AES generally (with cirl buntings being a notable exception; Kleijn et al. 2011),we consider it fair to use the evidence from the present study to conclude that AESmanagement does provide higher quality habitat for several non-target groups. The presentstudy has not tested the effects of landscape composition, which may modify the effects ofAES (di Giulio et al. 2001; Steffan-Dewenter et al. 2002; Kohler et al. 2008), although itsimportance relative to habitat quality is variable (Weibull and Ostman 2003; Holzschuh2006). There are not strong gradients of land use across the study area in the present study,although this may be an approach of interest in future.

The observed results are consistent with other studies of British AES; for example, areview of efforts to maintain, restore or re-create lowland grassland found that results weremore often favourable when management involved reductions in fertiliser and changes tograzing intensity (Critchley et al. 2003). For cirl bunting AES pasture fields, there is anelement of pre-selection bias, as these fields tended to be less recently ploughed thancontrols. In arable fields, many of the differences could be attributed to crop type ratherthan AES management. With the exception of the results for carabid beetles, the differ-ences in arable fields were between spring barley and winter cereal fields, while responsevariables did not differ between AES and control spring barley fields. However, as cirlbunting AES agreements would have increased the amount of spring barley in the land-scape, where otherwise farmers would have grown more winter cereals (Deborah Deveney,RSPB Cirl Bunting Project Officer, pers. comm.), we suggest that there may well be aneffect operating at the landscape scale.

Agri-environment management targeted at cirl buntings did not benefit every speciesgroup that was surveyed. Where it did, the differences were quite modest for some taxa.Benefits were limited compared to other bespoke AES options targeted at these taxa: forexample, pollen and nectar mixes for butterflies and bumblebees (although as whole-fieldoptions, smaller per unit benefits occur over larger areas). Nor were there great benefits forother rare species. None of these points should, however, detract from the general benefits

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to biodiversity demonstrated by this study, which arise from the general extensification offarm management, leading to an amelioration of the farmed landscape for some groups.Addressing the factors causing decline in one species (e.g. loss of spring-sown crops, lossof arable fields in the landscape and increased fertilisation of grass fields) might beexpected to have some benefits for other threatened species that share similar life historytraits (Barbaro and van Halder 2009). However, other rapidly declining, rare or scarcespecies may often require targeted initiatives of their own, tailored to addressing the causesof decline/limiting factors in a similar way to that which has been done through AESmanagement for cirl buntings.

Acknowledgments This project was funded by the RSPB and Natural England under the Action for Birdsin England partnership. The RSPB’s South West regional office provided valuable support during thecollection of field data. Adam Butler of BIOSS gave statistical advice. Martin Luff assisted with identifi-cation of some carabid specimens. Abigail Wooding identified bat calls. We are grateful to landowners andmanagers who allowed access to their properties. Two anonymous reviewers have made comments that haveimproved this manuscript.

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