use of set-aside land in winter by declining farmland bird species in the uk

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Use of set-aside land in winter by declining farmlandbird species in the UKD.L. Buckingham , A.D. Evans , A.J. Morris , C.J. Orsman & R. YaxleyPublished online: 29 Mar 2010.

To cite this article: D.L. Buckingham , A.D. Evans , A.J. Morris , C.J. Orsman & R. Yaxley (1999) Use of set-aside land inwinter by declining farmland bird species in the UK, Bird Study, 46:2, 157-169, DOI: 10.1080/00063659909461127

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© 1999 British Trust for Ornithology

Populations of many species of farmland birdhave declined in the UK over the past 25 years,both in numbers1 and range2 to such an extentthat they are of high conservation concern.3,4

Declining farmland species tend to share eco-logical features; with few exceptions the adultbirds feed on seeds in the winter and spring,while in the summer they feed their chicks oninsects.5,6 Eight farmland species which feedpredominately on seed in the winter declinedby more than 50% between 1969 and 1994.7

Over the past 50 years, price support mecha-nisms and technological development have ledto a rapid intensification of arable productionin the UK. This has involved wholesale changesin arable farming practice which are likely tohave had an adverse impact on seed-eatingbirds.8 These include the loss of mixed farming

enterprises and the associated loss of livestockfeed. One of the most important changes onlight soils is likely to have been the switch fromspring to autumn tillage and the associated lossof over-winter stubble fields which are a welldocumented source of winter seed foods.8

Agricultural subsidies and technologicaldevelopment made arable farming so efficientthat over-production became a problem in the1980s. A mechanism to control this, �set-aside�,was introduced, initially as a voluntaryscheme, in 1988. Reform of the CommonAgricultural Policy in 1992 made price supportconditional on arable farmers setting aside(leaving fallow) 15% (initially) of their landwhich had been in arable production.9 As aresult over 600 000 ha of land in the UK weretaken out of arable production in 1992.

Although the rules concerning managementof set-aside land have evolved every year sinceits introduction, there are two basic types: land

Bird Study (1999) 46, 157�169

Use of set-aside land in winter by declining farmlandbird species in the UK

DAVID L. BUCKINGHAM, ANDY D. EVANS*, ANTONY J. MORRIS,CHRIS J. ORSMAN and ROB YAXLEY Royal Society for the Protection ofBirds, The Lodge, Sandy, Bedfordshire SG19 2DL, UK

Between 1992 and 1993 over 600 000 ha of arable farmland in the UK were setaside under a production control mechanism of the Common AgriculturalPolicy (CAP) of the European Union. One of the management options for this set-aside land was to leave it as an over-winter fallow with a naturallyregenerated green cover. This study was designed to test whether such land wasused by seed-eating bird species, populations of many of which have undergonerecent severe declines. Five out of six declining species recorded in the studywere found in significantly greater numbers on this habitat than would beexpected if the birds were randomly distributed over the farmland landscape.The results of this study, covering a wide geographical area, reinforce previousfindings of the importance of winter food sources, particularly over-winterstubble fields, to declining farmland seed-eaters. Proposed changes to the CAPunder Agenda 2000 include the reduction of the obligatory set-aside rate to zero. These results suggest that such a move might be detrimental to populations of declining farmland birds. There is an urgent need for an agri-environment scheme designed to integrate arable production and conservation objectives, which operates in the wider countryside, includes pro-vision for over-winter stubble fields and is available to every arable farmer.

*Correspondence authorEmail: [email protected]

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taken out of production on a long-term basis(non-rotational) and land taken out for oneyear only (rotational).9 A green cover must beestablished on set-aside land to avoid leachingof nutrients (which can pollute groundwater).This can be achieved either by sowing or bynatural regeneration. In the latter case, a set-aside field in its first year is effectively identicalto a �traditional� stubble field left after the harvest of the preceding crop, the only differ-ence being that it remains fallow through the following summer. Thus set-aside mightbenefit declining farmland birds by providing awinter foraging habitat.

This study examined whether set-aside isselected as a foraging habitat by decliningfarmland birds in winter and what aspects ofthe management of set-aside land determinethe degree of any attraction.

METHODS

Study sites

Fieldwork was carried out between lateOctober and early March 1993/94 and 1994/95.The same 40 randomly selected farm plots weresurveyed in both winters. The selection wasstratified to comprise 20 plots in south Devonand 20 in East Anglia, so that half were repre-sentative of a traditional mixed arable/ pasturelandscape and half of an intensive arable land-scape respectively. Plots were centred onset-aside fields in the first winter and werebetween 50 and 100 ha in size. Thus, in Devon,plots comprised two or more holdings, whereas in East Anglia they typically fell within a single farm.

Bird counts

All species using each plot were counted threeor four times each winter by �complete areasearch� (cf. Wilson et al.10), walking paralleltransects up and down each field, including themargins, the transects being close enough toeach other to ensure all birds were flushed. Thismeant that the distance between transects varied with crop type, being greater on short,sparse crops and shorter on tall or dense crops.The maximum separation for transects was 50 m, so that the observer walked within 25 mof every point of the study plot. The choice of

distance between transects involved somedegree of subjectivity but in practice it was fairly clear whether or not all birds had beenflushed. The number of birds in each discreteflock was recorded separately for each species,individuals being recorded as a flock size ofone. If no birds were located on a field, a countof zero was recorded. Care was taken to avoiddouble-counting of birds which, when dis-turbed, flew to a field yet to be surveyed. Eachfield was treated as a separate unit unless therewere clearly two or more crop types within it;when each was counted separately.

Birds in field boundaries (structures such ashedgerows, fences and ditches separating adjacent fields) were recorded separately fromthose using the field or the margins (areasbetween the crop edge and boundary) andassigned to the field from which they wereobserved (unless clearly using the other side ofthe boundary). Birds flying over fields wereignored unless they were actively foraging. Foreach survey, the route was altered to avoidbiases due to time of day. Surveys were notconducted within one hour of dawn or dusk (toavoid movements to and from roosts) nor inconditions of continuous rain or winds aboveBeaufort force 4 (20�28 km/h). At least threeweeks separated successive counts on the sameplot.

Habitat records

On each visit, the crop type of each field orsubunit was recorded and the number of grazing animals and any evidence of grazingsince the last visit were noted. Details of set-aside management, the crop type prior to aparticular field being set aside and the age ofparticular fallows (whether or not they formedpart of the farmers set-aside requirement) wereobtained from the farmers. The length, heightand type of each boundary were recorded atthe start of each season. The area of each field(or subunit) was measured from a 1: 25 000map using a digitizer.

Analysis

There are two problems to overcome whendealing with winter bird counts collected usingthe above methods: (1) the data include manyzero counts; (2) individuals in flocks cannot be

158 D.L. Buckingham et al.

© 1999 British Trust for Ornithology, Bird Study, 46, 157�169

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Use of set-aside by wintering farmland birds 159

considered as independent data points. Toaddress these problems, and test the nullhypothesis that birds distributed themselvesrandomly with respect to the relative area ofavailable habitats, we used a method of resam-pling with replacement.10 This method is free ofany assumption about the statistical distribu-tion of the data collected. Each non-zero fieldcount acts as an independent datum in theanalysis; this is intermediate between theextremes of either assuming that every indi-vidual in a flock is acting independently orreducing the data to presence/absence for eachfield. We agree with Wilson et al.10 that thiscompromise is biologically realistic; birds willbe attracted by conspecifics in a flock and arethus unlikely to select foraging habitats inde-pendently, yet variation in the number of birdsusing particular habitat types is important inassessing their relative value as foraging sites.

Each region and winter were treated sepa-rately. Species for which there were more than20 non-zero field counts were included in theanalysis; the choice of cut-off is arbitrary butthe power of the resampling procedure todetect preference or avoidance will be reducedwith sample size. When analysing habitatselection, counts from the fields and marginswere included, those from boundaries ignored.For each species, all counts within each roundof visits to the 20 study plots in a region weretreated as a representative sample of the distri-bution of flock sizes on farmland during thosevisits. Count data were analysed for eachregion and winter separately using a resam-pling procedure. Non-zero counts were chosenat random, with replacement, from the countdata set for one round of visits at a time andassigned at random to a habitat present withinthat round of visits with a probability equal tothe proportion of the total area sampled in that round occupied by that habitat type. Thenumber of randomly selected counts assigned

within each visit equalled the number of non-zero counts within that round of visits.This procedure was repeated for all visitrounds and the habitat totals for each of thethree (or four) rounds of visits were then addedto produce a randomized distribution of counttotals across habitats in the region over thewhole winter.

The resampling procedure was repeated 1000times for each species in each region and winter. The median of the resampled valuesgave the expected number of birds that wouldhave been recorded on a given habitat if theyhad been foraging at random � the null hypoth-esis. The 25th and 975th values when rankedgave the 95% confidence intervals. Thus thereis only a 5% chance that the observed countexceeds these extremes. Where the observedtotal count for a species exceeded the upperconfidence limit, the species was interpreted asselecting that habitat; where it fell below thelower confidence limit, the species was interpreted as avoiding the habitat. For rarehabitats, the 95% confidence intervals can reachzero, so it is not always possible to demonstrateavoidance.

RESULTS

Regional variation in farm structure and crop type

The availability of habitats differed betweenregions, reflecting the differences in farmingpractice. East Anglia is dominated by cerealproduction and sugar beet whereas Devon is a mixed arable/pastoral region with a high proportion of grass fields. Farms variedbetween regions in their structure as well as the habitat types they offered. The mean field size was far larger in East Anglia thanDevon (Table 1) and in consequence Devon hada greater boundary length per unit area

Table 1. Size of fields and number of visits by region.

Number Total area Mean area Number of Total Total areaRegion Year of Fields (ha) (ha) visits field visits searched (ha)

Devon 1993/94 509 1286.5 2.53 3 1527 38601994/95 518 1192.3 2.30 3 1554 3577

East Anglia 1993/94 200 1354.5 6.77 4 800 54181994/95 177 1292.3 7.30 3 531 3877

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(170 versus 114 m/ha) and a greater volume of hedgerow per unit area (1360 versus 643 m3/ha) than East Anglia.

Variation in set-aside availability and management between regions and years

The relatively high availability of set-aside inthe first winter (21% in Devon, 29% in EastAnglia, despite the fact that the rate required toreceive price support was only 15%) was due tothe fact that the chosen plots were centred onset-aside fields. In the second winter theamount of set-aside fell to 11% in Devon and14% in East Anglia as rotational set-aside wasoften moved to fields outside the study plots.

The availability of the four basic set-asideoptions varied between regions and years (Fig. 1). Rotational set-aside with a naturallyregenerated cover was the most popular optionin East Anglia, some two or three times morecommon than in Devon. More farmers in

Devon established a green cover by sowingthan by natural regeneration (over 50% in1994/95). Also, where green cover was estab-lished by sowing in East Anglia, it tended to bebrassicas rather than grass. In this region in thesecond winter, rotational and non-rotationalset-aside land were equally available, while inEast Anglia the rotational option accounted for70% of land in set-aside.

In both regions, non-set-aside stubblesaccounted for 5�17% of the area searched at thebeginning of the winter but this fell to 3�4% bythe final visit. In contrast, the area of set-asidestubble remained constant throughout the winter. In 1993/94, set-aside stubbles account-ed for 59% (East Anglia) and 64% (Devon) of allfirst-year naturally regenerated fallow at thebeginning of the winter. By the final visits,these figures had increased to 87% and 74%,respectively, as the non-set-aside stubbles werecultivated.

In Devon, in the first winter, barley was themost common crop preceding first-year fallows(including non-set-aside fields) accounting for74% of the total area. There was a more evendistribution of preceding crop type in the second winter, with barley at 29%, wheat 14%and linseed 27%. In East Anglia in both years,similar areas of wheat (33% and 22%) and barley (32% and 35%) were left fallow after harvest. Winter grazing of fallows includingset-aside was fairly common in Devon (12%and 36% of the fallow area in the two winters)but rare in East Anglia (5% and 1%).

Regional variation in bird counts

Table 2 shows the total number of registrationsby winter for those species with more than 20 non-zero field and margin counts in at leastone winter/region and Table 3 the percentageof non-zero field and margin counts. There aresome large differences between regions.

Count data were highly skewed with a high percentage of zero counts. Skylark was themost ubiquitous species, encountered onbetween 17 and 30% of field visits (Table 3). Toincrease sample sizes, species were aggregatedinto the biological groups shown in Table 2.

Habitat selection

In the following summary, a species is regarded



East Anglia 1993/94(393 ha)

East Anglia 1994/95(167 ha)

Devon 1993/94(258 ha)

Devon 1994/95(138 ha)

SA2G20%

SA1G29% SA2R

7%

SA1R44%

SA2G26%

SA1G29%

SA2R22%

SA1R23%

SA2G2%SA1G

12%

SA1R86%

SA2G17%SA2R

13%

SA1R70%

Figure 1. Proportion of set-aside type by region andyear. SA1R, First-year set-aside with green coverestablished by natural regeneration; SA1G, first-yearset-aside with green cover established by sowing;SA2R, second-year or older set-aside with greencover established by natural regeneration; SA2G, second-year or older set-aside with green coverestablished by sowing.

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as selecting or avoiding a habitat if observedmore or less often than expected in one or bothwinters. There were only two instances of aspecies showing selection in one year andavoidance in the other: Pheasant on first-yearset-aside with a sown green cover in EastAnglia and Carrion Crow on arable in Devon.

Devon

Twenty-one species were recorded sufficiently

frequently in Devon to have their distributionassessed by resampling (Fig. 2). Of these, 15 occurred less frequently on arable (wintercereal and plough) in one or both winters thanexpected if their distribution was random withrespect to habitat. Similarly, 14 showed anavoidance of grass. First-year natural regenera-tion fallows (both set-aside and non-set-asidestubbles) were used more than expected by 11species and less than expected by three. Olderset-aside fields were not preferred, although



Table 2. Total winter field and margin counts (across all visits) for those species and species groups encounteredsufficiently regularly for analysis of distribution by resampling (>20 non-zero counts). Visits 1�3 only given forEast Anglia 1993/94 so figures can be compared between years and regions.

Devon East Anglia

Species 1993/94 1994/95 1993/94 1994/95

Red-legged Partridge 0 19 769 826Grey Partridge 18 9 304 119Pheasant 169 132 458 294Black-headed Gull 705 828 558 1037Woodpigeon 662 963 3780 2242Skylark 7041 3545 3425 2454Meadow Pipit 1239 1655 674 147Pied Wagtail 383 163 266 49Wren 428 283 6 17Dunnock 578 495 38 36Robin 393 298 16 11Blackbird 522 410 62 38Song Thrush 495 641 7 42Redwing 135 207 20 46Mistle Thrush 17 19 55 54Magpie 334 286 28 23Jackdaw 551 501 375 342Rook 1265 876 1015 211Carrion Crow 474 269 37 27House Sparrow 291 171 0 24Chaffinch 2426 1058 854 253Greenfinch 219 55 116 237Goldfinch 566 1768 39 172Linnet 1906 1615 674 558Yellowhammer 358 337 910 433Cirl Bunting 378 283 0 0

Species groupsWaders 260 215 816 218Gulls 1337 1244 891 1082Raptors 89 72 27 21Gamebirds 187 160 1826 1239Pigeons 880 1224 5165 2407Corvids 2642 1956 1576 606Robin/Wren/Dunnock 1399 1076 72 64Thrushes 1320 1350 1092 739Finches/sparrows/buntings 6206 5350 3490 1718

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those sown to grass were selected by Skylark,Meadow Pipit, Goldfinch and Cirl Bunting.Root crops and brassicas were preferred byseven species and avoided by two. Nine speciesfavoured scrub and orchard; only two (Skylarkand Meadow Pipit) avoided this habitat.

In order to simplify the overall picture,resampling was undertaken on the speciesgroups shown in Table 2 (Fig. 3). Finches, spar-rows and buntings (seed-eaters) showedselection for first-year naturally regeneratedfallows in both years, pigeons and gamebirdsin only one of the two seasons. Root crops andbrassicas were selected by the seed-eaters andgame birds but also by thrushes and the group containing Robin, Wren and Dunnock(primarily insectivores). The last two groupswere also found more often than expected inscrub and orchards (as were gamebirds), butavoided first-year fallows. Arable and grasswere generally avoided by all groups exceptwaders, gulls and pigeons.

East Anglia

Of the 16 species in East Anglia which wereresampled, 12 avoided winter cereal orploughed fields; only roosting Black-headedGulls selected this crop-type (Fig. 4). First-yearnaturally regenerated fallows were used moreoften than expected by seven species and first-year sown grass set-aside was used more oftenthan in Devon (five as opposed to three speciespreferred it). Spring-sown cereals (mainlymaize and gamestrips) were selected by fivespecies but winter cereals and plough avoidedby 12.

East Anglia differed from Devon in the distribution of species groups. Finches, spar-rows and buntings were concentrated onsecond-year naturally regenerated fallows orfirst-year fallows that had a sown cover. Arablewas avoided by this group and by gamebirds,pigeons, raptors and Robin, Wren andDunnock. Robin, Wren and Dunnock preferred



Table 3. Percentage of the total number of winter field and margin counts that were greater than zero for thosespecies encountered sufficiently regularly for analysis of distribution by resampling (>20 non-zero counts).

Devon East Anglia

Species 1993/94 1994/95 1993/94 1994/95

Red-legged Partridge 0 0 25 26Grey Partridge 0 0 7 4Pheasant 7 5 18 16Black-headed Gull 3 2 6 3Woodpigeon 4 6 13 11Skylark 17 17 30 26Meadow Pipit 14 14 13 8Pied Wagtail 5 2 6 2Wren 15 12 0 0Dunnock 15 16 4 4Robin 14 14 2 2Blackbird 14 15 8 5Song Thrush 12 15 2 4Redwing 1 1 1 2Mistle Thrush 1 1 4 5Magpie 9 7 2 2Jackdaw 3 2 2 1Rook 3 2 2 2Carrion Crow 8 8 2 2House Sparrow 2 1 0 0Chaffinch 9 8 8 6Greenfinch 2 1 3 2Goldfinch 4 5 2 1Linnet 4 3 4 3Yellowhammer 5 3 9 7Cirl Bunting 5 4 0 0

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root crops and brassicas, and spring cereal,which was also selected by gamebirds (Fig. 5).In East Anglia, first-year fallows with naturalregeneration were not selected except by game-birds and pigeons.

Selection of non-stubble set-aside fields

Preferences for other types of set-aside were



also shown by some species, although no clearpatterns emerged. In Devon, first-year sowngrass fields were used by Meadow Pipit, PiedWagtail and Chaffinch, and in East Anglia byChaffinch but also Pheasant, Skylark, Linnetand Yellowhammer. Old naturally regeneratedcover was used by Skylark, Linnet andYellowhammer in East Anglia, and by CirlBunting in Devon. Old grass cover was used by

SA1R SA2R SA1G SA2G NS1R NS2R ARAB VEGY GRAS SSC OIL SHRB REST1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2

Pheasant N N NBlack-headed gull N N NWoodpigeon N N NSkylark N N NMeadow pipit N N NPied wagtail N N NBlackbird N N NSong thrush N N NRedwing N N NMistle thrush N N NMagpie N N NJackdaw N N NRook N N NCarrion crow N N NHouse sparrow N N NChaffinch N N NGreenfinch N N NGoldfinch N N NLinnet N N NYellowhammer N N NCirl bunting N N N

Figure 2. Results of resampling procedure for species in Devon 1993/94 (1) and 1994/95 (2). Black squares indicate crops used to a greater extent than expected from a random distribution of the count data (P < 0.05, two-tailed). Grey squares indicate crops used to a lesser extent than expected from a random distribution of the countdata (P < 0.05, two-tailed). White squares indicate pattern of use not significantly different from random. N, Habitat option not available or species not recorded in that region/year. SA1R, First-year set-aside with greencover established by natural regeneration; SA1G, first-year set-aside with green cover established by sowing;SA2R, second-year or older set-aside with green cover established by natural regeneration; SA2G, second-yearor older set-aside with green cover established by sowing; NS1R, first-year non-set-aside fallow with green cover established by natural regeneration; NS2R, second-year or older non-set-aside fallow with green cover established by natural regeneration; ARAB, winter cereal and bare plough; SSC, spring sown cereal (largely maize and gamestrips); GRAS, all pasture; OIL, oil-seed rape and linseed; SHRB, scrub and orchards;REST, all other.


Waders N N NGulls N N NRaptors N N NGamebirds N N NPigeons N N NCorvids N N NRobin/wren/dunnock N N NThrushes N N NFinches/sparrows/buntings N N N

Figure 3. Results of resampling procedure for groups in Devon 1993/94 (1) and 1994/95 (2). Species groupedroughly by family. Black squares indicate crops used to a greater extent than expected from a random distribu-tion of the count data (P < 0.05, two-tailed). Grey squares indicate crops used to a lesser extent than expectedfrom a random distribution of the count data (P < 0.05, two-tailed). White squares indicate pattern of use not significantly different from random. N, Habitat option not available or species not recorded in that region/year.Crop codes as for Fig. 2.

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Grey Partridge, Meadow Pipit and Goldfinchin East Anglia and by Meadow Pipit, Skylark,Goldfinch and Cirl Bunting in Devon. Resultsof these habitat selection analyses are summa-rized in Table 4.

Declining species

Further resampling was carried out on simpli-

fied habitat categories, including all fallows, forsix declining species (Fig. 6). Five of these: GreyPartridge, Linnet, Skylark, Yellowhammer andCirl Bunting selected fallow (whether set-asideor not). The only declining species that did notselect fallow was Song Thrush. All avoidedarable in at least one region/winter and pasture in Devon. Song Thrush and Linnetselected cash crops (predominantly oil-seeds,root crops and vegetables).

Influence of previous crop on the selection of first-year fallows

Figure 7 shows the pattern of selection of first-year fallows according to the crop grown in thefield immediately before the set-aside periodcommenced. In both regions, set-aside stubblesresulting from barley crops were more stronglyselected than those from wheat. Stubbles frompea, oilseed rape and linseed crops were alsowell used in Devon while those from maizewere selected by finches and buntings in EastAnglia.

Influence of winter grazing on the selectionof first-year fallows

From Fig. 8, it appears that first-year fallowswith natural regeneration are more attractive toseed-eating species if the field is not grazed. Forfirst-year sown green cover, grazing appears toincrease bird selection in East Anglia for threeof the five bird groups.




Red-legged partridge N N N NGrey partridge N N N NPheasant N N N NBlack-headed gull N N N NWoodpigeon N N N NSkylark N N N NMeadow pipit N N N NPied wagtail N N N NBlackbird N N N NSong thrush N N N N N N N N N N N N N NMistle thrush N N N NChaffinch N N N NGreenfinch N N N NGoldfinch N N N N N N N N N N N N N N N NLinnet N N N NYellowhammer N N N N

Figure 4. Results of resampling procedure for species in East Anglia 1993/94 (1) and 1994/95 (2). Black squaresindicate crops used to a greater extent than expected from a random distribution of the count data (P < 0.05, two-tailed). Grey squares indicate crops used to a lesser extent than expected from a random distribution of the countdata (P < 0.05, two-tailed). White squares indicate pattern of use not significantly different from random. N,Habitat option not available or species not recorded in that region/year. Crop codes as for Fig. 2.

Table 4. Number of species found more and less frequently than expected on each crop type in at leastone winter than if distributed randomly. Figures inbrackets show the number of species of the 21analysed in Devon and the 16 in East Anglia forwhich it was possible to demonstrate avoidance.Crop codes as for Fig. 2.

Devon East Anglia

More Less More LessCrop often often often often

SA1R 6 3 (17) 6 0 (16)SA2R 1 0 (4) 3 0 (0)SA1G 3 1 (12) 5 1 (4)SA2G 4 4 (7) 2 0 (0)NS1R 10 1 (10) 2 2 (11)NS2R 2 0 (0) 2 0 (1)ARAB 1 15 (21) 1 12 (16)VEGY 7 2 (14) 4 1 (12)GRAS 0 14 (21) 1 1 (1)SSC N N 5 0 (0)OIL 3 0 (0) 2 0 (11)SHRB 9 2 (7) N NREST 3 0 (0) 0 0 (0)

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DISCUSSION

Regional variation in bird counts

Some of the differences in counts betweenregions (e.g. Cirl Bunting, Grey Partridge) canbe explained by the current geographical rangeof species. Other species (e.g. Dunnock,Chaffinch) may have been more common in Devon because of the difference in farmstructure, in particular the far higher hedgerowvolume per unit area in this county. Table 5shows that eight out of nine species associatedwith hedgerows were registered more frequently in Devon than in East Anglia.

However, these differences cannot beexplained by hedgerow structure alone, as theproportion of registrations involving indi-viduals in the field and margin rather than theboundary was higher in Devon than EastAnglia for seven of these nine species. This suggests that the opportunities to forage in




Waders N N N NGulls N N N NRaptors N N N NGamebirds N N N NPigeons N N N NCorvids N N N NRobin/wren/dunnock N N N NThrushes N N N NFinches/sparrows/buntings N N N N

Figure 5. Results of resampling procedure for groups in East Anglia 1993/94 (1) and 1994/95 (2). Speciesgrouped roughly by family. Black squares indicate crops used to a greater extent than expected from a randomdistribution of the count data (P < 0.05, two-tailed). Grey squares indicate crops used to a lesser extent thanexpected from a random distribution of the count data (P < 0.05, two-tailed). White squares indicate pattern ofuse not significantly different from random. N, Habitat option not available or species not recorded in thatregion/year. Crop codes as for Fig. 2.

Devon

Fallow Arable Pasture SSC Cash Other1 2 1 2 1 2 1 2 1 2 1 2

Grey partridge no dataSkylarkSong thrushYellowhammerLinnetCirl bunting

East Anglia

Fallow Arable Pasture SSC Cash Other1 2 1 2 1 2 1 2 1 2 1 2

Grey partridgeSkylarkSong thrushLinnetYellowhammerCirl bunting no data

Figure 6. Results of resampling procedure on simpli-fied habitat categories. Fallow includes fields underset-aside; Arable, winter cereal and plough; Pasture,all grass; SSC, spring sown cereal; Cash, cash crops,predominantly root crops and vegetables.

Table 5. Proportion of total winter registrations in 1994/95 of nine hedgerow species in the field and margin asopposed to the boundary by region. *** P < 0.001.

Devon East Anglia

Total incl. Field + Total incl. Field +Species boundary margin % boundary margin % χ2

Wren 1088 283 26 207 17 8 29.96***Dunnock 1004 495 49 181 36 20 54.84***Robin 1196 298 25 243 11 5 51.72***Blackbird 989 410 41 380 38 10 121.96***Song Thrush 1137 641 56 74 42 57 0.03 nsMistle Thrush 30 19 63 69 54 78 3.26 nsBlue Tit 324 63 19 281 18 6 20.95***Great Tit 128 31 24 84 11 13 3.28 nsChaffinch 1575 1058 67 778 253 33 252.01***

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fields may be greater in Devon for thesespecies.

Patterns of habitat use

Broad patterns of habitat selection emerged inthis study. The most obvious of these was the

almost universal avoidance by farmland birdsof winter cereals and plough. This is probablydue to of the lack of seed and invertebrate foodin this crop type. Wilson et al.10 found a similarpattern of avoidance of winter cereals andplough (except in early winter). In Devon pasture was avoided by 14 species and not



Devon

barl sbar whea lins oils veg& bare legs maize1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2

Skylark N 0 N NLinnet N N NYellowhammer N N NCirl bunting N N NFinches/sparrows/buntings N N N

East Anglia

barl sbar whea lins oils veg& bare legs maize1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2

Grey partridge N NSkylark N NLinnet N NYellowhammer N NFinches/sparrows/buntings N N

Figure 7. Results of resampling procedure for (1) 1993/94 and (2) 1994/95. First-year fallows only, grouped bythe prior crop type. Black squares indicate crops used to a greater extent than expected from a random distribu-tion of the count data (P < 0.05, two-tailed). Grey squares indicate crops used to a lesser extent than expectedfrom a random distribution of the count data (P < 0.05, two-tailed). White squares indicate pattern of use not significantly different from random. N, Habitat option not available or species not recorded in that region/year.Barl, barley; Sbar, spring barley; whea, wheat; lins, linseed; oils, oilseed rape; veg&, vegetables, brassicas androots; bare, bare fallow; legs, legumes.

Devon

1st yr sown 1st yr regen >1 yr sown >1 yr regenG U G U G U G U

1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2SkylarkLinnetYellowhamerCirl buntingFinches/sparrows/buntings

East Anglia

1st yr sown 1st yr regen >1 yr sown >1 yr regenG U G U G U G U

1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2Grey partridge N N N N N NSkylark N N N N N NLinnet N N N N N NYellowhamer N N N N N NFinches/sparrows/buntings N N N N N N

Figure 8. Results of resampling procedure for (1) 1993/94 and (2) 1994/95. Fallows only, (set-aside and non-set-aside) grouped by grazing regime: G, grazed; U, ungrazed. Black squares indicate crops used to a greaterextent than expected from a random distribution of the count data (P < 0.05, two-tailed). Grey squares indicatecrops used to a lesser extent than expected from a random distribution of the count data (P < 0.05, two-tailed).White squares indicate pattern of use not significantly different from random. N, Habitat option not available orspecies not recorded in that region/year.

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selected by any, whereas in East Anglia pasturewas too scarce to demonstrate avoidance byany species and only Blackbird selected it.These findings were in contrast to those ofWilson et al.10 who found that although seed-eaters avoided both grazed and ungrazedgrassland, eight invertebrate-feeding speciespreferred grazed grass. This difference may bedue to the more intensive management ofgrassland in Devon (in terms of inputs andstocking rates) than in Oxfordshire. Wilson etal.10 also incorporated organic farms in theirstudy; it is likely that organic grassland supports a higher biomass of soil invertebratesthan conventional grassland. Insectivores andthrushes selected orchards and scrub in Devon;these habitats are often associated with anunimproved grass sward. This study also illustrated the importance of brassicas and root crops to a range of species (especiallyinsectivores and thrushes, particularly SongThrush) in Devon.

Stubble-fields are an important habitat forfarmland seed-eaters in winter.7,11,12 Wilson etal.10 demonstrated that the winter distributionsof several species of seed-eating bird, includingGreenfinch, Reed Bunting, Linnet, Chaffinch,Yellowhammer, Goldfinch, Skylark and GreyPartridge were highly skewed towards stubble-fields. In this study, stubble-fields left as part ofthe crop rotation were used to a large extent byseed-eating birds in Devon, including threespecies of high conservation concern, Skylark,Linnet and Cirl Bunting.

In East Anglia, only Grey Partridge andSkylark used this habitat type to a greaterextent than expected. In both regions, how-ever, rotational set-aside with a naturallyregenerated green cover (which is essentiallyan over-winter stubble field) was used to agreat extent by several species. These includedthe declining species Skylark and Yellow-hammer in both regions, Grey Partridge in East Anglia and Linnet and Cirl Bunting inDevon. There is evidence that those stubblescreated from barley fields are selected overthose from wheat; why this should be so isunclear. It may relate to the annual arable plantpopulation in the fallow; a function of the richness of the seed bank and the recent agricultural management of the field. Grazingof first-year naturally regenerated fallowsmakes them less attractive to seed-eating birds.

Conservation value of set-aside

Of the six declining species recorded suffi-ciently often for analysis, only Song Thrushshowed no preference for fallow land. GreyPartridge, Skylark, Linnet, Yellowhammer andCirl Bunting all showed a preference for fallow(mainly set-aside) land in at least one winterand one region (Figs 6a & 6b). Set-aside landcan alter the distribution of birds in the winterfarmland landscape but does it have any valuefor conservation? To answer this question, itwould be necessary to measure the over-wintersurvival rates of the species of conservationconcern both before and after set-aside wasintroduced: a practical impossibility. If, how-ever, the strong selection for set-aside shown bysome of the species was indeed translated into over-winter survival, then it might be reasonable to expect amelioration in the rates ofpopulation decline, given the huge area of landtaken out of production. There are two sourcesof data giving populations post-1992: theBTO/JNCC Common Birds Census and theBTO/JNCC/RSPB Breeding Bird Survey; theseare summarized in Table 6, with additionalRSPB data for Cirl Bunting. Grey Partridge,Linnet and Cirl Bunting all selected set-asideland in this study and their population declineshave slowed (indeed UK populations of Linnetand Cirl Bunting are increasing. Skylark alsoselected set-aside land strongly but the evidence for an amelioration in the decline isless convincing. Song Thrush declines haveapparently slowed but the species did notselect set-aside. Yellowhammer selected set-aside but, after a long period of stability, thepopulation began a steep decline in the late1980s, which is apparently accelerating.

It is clear that if the right management is followed, set-aside land can produce a sourceof winter food for several declining farmlandbird species and this production control mech-anism may have (unintentionally ) benefitedsome populations. The importance of set-asideincreases through the winter, as stubble fieldsleft as part of the rotation are increasinglyploughed up. The consistent reduction in therequired set-aside rate and the decline in theproportion of rotational set-aside with naturalregeneration were giving cause for concern, butmore profound changes are likely.

In July 1997, the European Commission



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announced proposals to reform the CommonAgricultural Policy (Agenda 2000). These proposals include the reduction of the set-asiderequirement to zero in order to compensatefarmers for a reduction in the guaranteed pricesfor cereals. Set-aside will remain as a voluntaryoption as part of an agri-environment packagebut, unless another mechanism which acts onthe same geographical scale is put in place,population declines of farmland seed-eatingbirds are likely to continue or worsen.

In spring 1998, the UK government imple-mented the Arable Stewardship Pilot Schemewhich offers farmers a menu of costed prescriptions designed to benefit biodiversity.Individual farmers in the two pilot areas canchoose from this menu and receive paymentsfor implementing the conservation measures.The prescriptions were based on advice fromRSPB, the Game Conservancy Trust andEnglish Nature and include provision for leaving over-winter stubble fields. Increasedpayments are available for stubbles left fromcrops not treated with herbicides in the expec-tation that this will result in increasedavailability of non-crop seeds for winteringbirds. Additionally there are prescriptions forother ways of providing winter food, such asplanting cover crops including seed-rich mixtures.

Further prescriptions to provide invertebratefood and nest-sites in the breeding season alsoexist. Bird populations will be monitored onfarms within and without the scheme. If theprescriptions are successful in increasing localbird populations, and the results of this studysuggest that this will be the case for somespecies, it is hoped that the scheme will be

extended so that it is available to every arablefarmer in the UK. Such a move would providea realistic long-term solution to the problemsfacing our farmland wildlife and allow farmersto produce food and conservation objectives atthe same time.

ACKNOWLEDGEMENTS

We thank all the farmers who gave us access totheir land. We are particularly grateful to JerryWilson for advice over analysis. The manu-script was improved by comments from MarkAvery, Lennox Campbell, Jerry Wilson, KenNorris and an anonymous referee.

REFERENCES

1. Marchant, J.H., Hudson, R., Carter, S.P. & Whit-tington, P. (1990) Population trends in BritishBreeding Birds. BTO, Tring.

2. Gibbons, D.W., Reid, J.B. & Chapman, R.A. (1993)The New Atlas of Breeding Birds in Britain and Ire-land: 1988�1991. T. & A.D. Poyser, London.

3. Gibbons, D., Avery, M., Baillie, S., Gregory, R.,Kirby, J., Porter, R., Tucker, G. & Williams, G.(1997) Bird Species of Conservation Concern inthe United Kingdom, Channel Islands and the Isleof Man: revising the Red Data List. RSPB Conserv.Rev., 10, 7�18.

4. Anon. (1995) Biodiversity: The UK Steering GroupReport. Vol. 1, Meeting the Rio Challenge. HMSO,London.

5. Campbell, L.H., Avery, M.I., Donald, P.J., Evans,A.D., Green, R.E. & Wilson, J.D. (1997) A Review ofthe Indirect Effects of Pesticides on Birds. JNCCReport No. 227.

6. Wilson, J.D., Arroyo, B.E. & Clark, S.C. (1997) TheDiet of Bird Species of Lowland Farmland: a LiteratureReview. Unpublished report by BBSRC-NERC for



Table 6. UK population trends of declining farmland birds after 1992.

BoCCa Selects Pop. trend Pop. trend BBS trend DeclineSpecies status fallow? 1971�95c 1992�95e 1994�96f slowed?

Grey Partridge Red Yes �86 = + YesSkylark Red Yes �61 � = Not clearSong Thrush Red No �70 + = YesLinnet Red Yes �49 + = YesYellowhammer Greenb Yes �24 � � NoCirl Bunting Red Yes �83d + No data Yes

aBirds of Conservation Concern status (see ref. 3). bWould now qualify as red with a decline of 60% between 1971and 1996 (BTO data). cBTO Common Birds Census data. dRSPB data. eFrom visual inspection of CBC trend.fBTO/JNCC/RSPB Breeding Bird Survey data.

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accident....and design? RSPB Conserv. Rev., 11,59�66.

10. Wilson, J.D., Taylor, R. & Muirhead, L.B. (1996)Field use by farmland birds in winter: an analysisof field type preferences using resampling meth-ods. Bird Study, 43, 320�332.

11. Evans, A.D. & Smith, K.W. (1994) Habitat selec-tion of Cirl Buntings Emberiza cirlus wintering inBritain. Bird Study, 41, 81�87.

12. Donald, P. F. & Evans, A.D. (1994) Habitat selec-tion by Corn Buntings Miliaria calandra in winter.Bird Study, 41, 199�210.



DoE, JNCC & EN.7. Evans, A.D. (1998) Seed-eaters, stubble fields and

set-aside. Proc. Brighton Crop Protection Conference1997, 907�914.

8. Evans, A.D. (1997) The importance of mixed farm-ing for seed-eating birds in the UK. In Farming andBirds in Europe. The Common Agricultural Policy andIts Implications for Bird Conservation (eds D. Pain &M.W. Pienkowski) pp. 331�357. Academic Press.London.

9. Evans, A.D., Curtoys, J., Kew, J., Lea, A. & Ray-ment, M. (1998) Set-aside: Conservation by

(MS received 9 October 1997; revised MS accepted 20 July 1998)

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use of set-aside land in winter by declining farmland bird species in the uk

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