Poland Farmland in bird contrasting diversity agricultural landscapes ofsouthwestern Landscape and Urban Planning

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Landscape and Urban Planning

jou rn al h om ep a ge :w w w . e l s e v i e r . c o m / l o c a t e / l a n d u r b p l a n

Farmland bird diversity in contrasting agricultural landscapes of southwestern Poland

Andrzej Wuczy ´nski

^∗

PolishAcademyofSciences,InstituteofNatureConservation,Lower-SilesianFieldStation,Podwale75,Wrocław50-449,Poland

h i g h l i g h t s

•AgriculturallandscapesofPolandsupportdensepopulationsofbreedingbirds.

•Highbirdabundancesarestronglyrelatedtoadiversenetworkofﬁeldmargins.

•Noncroppedhabitatsaremoreimportantforbiodiversitythanland-usediversiﬁcation.

•Densityofshrubbymarginsisausefulpredictorofoverallbiodiversityinfarmlands.

•Preventinglandscapesimpliﬁcationshouldbeapriorityincomplexagroecosystems.

a r t i c l e i n f o

Articlehistory:

Received30May2014

Receivedinrevisedform16October2015 Accepted6November2015

Keywords:

Farmlandbirds Fieldboundaries Landscapestructure Habitatselection Land-usemosaic CentralEurope

a b s t r a c t

BreedingbirdcommunitieswereinvestigatedinthreecontrastingagriculturallandscapesofSWPoland toassessdifferencesinabundanceanddeterminetheimportanceofﬁeldmarginsforbirdpopulations.

Countswereconductedintwelve50-haplotsdifferinginlandscapestructure(densityofall,permanent andshrubbyfieldmargins,andoccurrenceofhighvegetation).Mapsofbirddistributionswereused toanalyzetheassociationsofbirdswithfourhabitats:croppedfields,permanentfallows,fieldmargins,mid-fieldwoodlots.Ordinationandclassificationtechniqueswereappliedtocheckbetween-plot differencesincommunitycomposition.Alllandscapessupportedhighdensitiesoftotalcommunities andfarmlandspecialists.Speciesrichnessandbirddensitiesweresignificantlyrelatedtofieldmargin aggregationsandarrangedalongadecreasinggradientoflandscapeheterogeneity:shrubbymosaic,open mosaic,openplainplots.Between-plotdifferencessuggestthattheoccurrenceofnon-croppedhabitats ismoreimportantforbirdabundancethandiversificationofland-use.PCAandclusteranalysisidentified differencesinspeciescompositionbetweenthelandscapetypes;andRDArevealedthesignificanceof theshrubbyandpermanentmarginsforthecommunitystructure.Theaggregationofshrubbymargins seemstobeaparticularlyusefulpredictorofbirdabundanceandoverallbiodiversity.Mostspeciesand breedingpairswerepreferentiallyassociatedwithmargins,despitethehabitatcoveringmerely4%ofthe area.Thedataconfirmedthatlandscapeheterogeneitywithmosaicseminaturalfieldmarginsisrespon- sibleforthepersistenceofinternationallyimportantbirdpopulationsinPoland.Insuchcomplexarable systems,preventinglandscapesimplificationisthemosteffectivemethodofbiodiversityprotection.

1. Introduction

Duetoenvironmentalheterogeneity,farmedlandscapesbelong tothemostbiodiversity-richlandscapesinEurope.Atthesame time,inmanytaxadramaticdeclinesoffarmlandpopulationshave beendocumented(deHeer, Kapos,&tenBrink,2005)and per- sistdespitehugepolicyandﬁnancialpreventiveefforts,suchas

∗ Tel.:+48713376349.

E-mailaddress:a.wuczynski@pwr.edu.pl

agri-environmentschemes(AES)(Santanaetal.,2014).Birdcom- munitiesarecommonlyusedtodocumenttheseprocesses,and toquantifythehealthofoverallfarmlandbiodiversity.However, boththebirdpopulationmetricsandextentofdeclinesarehighly unevenamongregions,andthosewithretainedtraditionalfarming systemsareofparticularimportanceforagriculturalbiodiversity (Báldi & Batáry, 2011; Billeter et al., 2008; Kleijn et al., 2009;

Tryjanowskietal.,2011).Therefore,ithasbeenagreedthattopro- tectbiodiversityoverlarger(e.g.,continental)scaleconservation, methodsshouldbebettertailoredtoregionalbiodiversityindices and farming circumstances (Concepción et al., 2012; Jongman, http://dx.doi.org/10.1016/j.landurbplan.2015.11.010

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2002;Tscharntke,Klein,Kruess,Steffan-Dewenter,&Thies,2005;

Winqvistetal.,2011).Unfortunately,evidenceregardingbirdabun- danceandneeds(i.e.,thebaseforreliablerecommendations)isalso notproportionaltobiodiversityresources.Thebulkofornitholog- icaldataandconservationproposalscomefromwesternEurope with many declining bird populations, whereas evidence from otherbiogeographicregionsthataredisproportionatelyricherin biodiversity,suchas Centraland EasternEurope(CEE),are still insufﬁcient,yetgrowing(Báldi,Batáry,&Kleijn,2013;Herzon&

O’Hara,2007;Mander,Mikk,&Külvik,1999;Reif,Voˇríˇsek, ˇStastn ´y, Bejˇcek,&Petr,2008;Sutcliffeetal.,2015).

Thepresent studywasconducted inone ofsuchregions, in Poland, and examined how thecommunities of breedingbirds respondto differentlevels of landscape complexity. The coun- tryisparticularlysuitableforthiskindofanalyzes,givenalarge areaof farmland (>180,000km²), the existing types of agricul- ture,andaninternationallyimportantbiodiversity(Kuczy ´nski&

Chylarecki,2012;Tryjanowski,Ku ´zniak,Kujawa,&Jerzak,2009).

Atthesametime,theagriculturallandinPolandissubjecttounidi- rectional,detrimentaltransformationsdrivenbyeconomicgrowth, butalsobyagriculturalpolicyafterenteringtheEuropeanUnion (EU)(Sanderson,Kucharz,Jobda,&Donald,2013).Thesechanges arelikelytoincreaseandaffectthebiodiversityinalarger,regional scale;therefore,up-to-dateecologicaldatafromspecies-richfarm- landsarerequiredforevidence-basedactionstobemade.

The landscape complexity in this studyhas been expressed through the common presence of field margins which are an important featureof thePolish agriculturallandscapes. Indeed, inbirdsrecentcountry-scaleevidenceindicatesthatamongnine measuresofagriculturalmanagementthewoodyedgehabitatsin Poland,suchastreelinesandhedgerows,werethemostconsis- tentpredictor ofoverall speciesrichness and richness oftarget groups,suchasspeciesofconservationconcernandfarmlandspe- cialists(Sanderson,Kloch,Sachanowicz,&Donald,2009).Several habitat-scalestudiesalsoconfirmedthatfieldmarginsinPolandare inhabitedbyrichanddiversecommunitiesofbirdsandothertaxa, includingregularoccurrenceofthreatenedspecies(Ł ˛ecki,2004;

Szyma ´nski & Antczak,2013; Wuczy ´nski, Dajdok, Wierzcholska,

&Kujawa, 2014).However, theimportance of field margins in a broader landscapeperspective hasrarely beenstudied. Thus, thereareinsufficientdataquantifyingtheproportionofbirdcom- munitiessupportedbymargins,andoverallhabitatassociations offarmlandbirds(Herzon,Auninˇs,Elts,&Preikˇsa,2006;Skórka, Martyka,&Wójcik,2006).Actually,thisisthefirststudyIknowof thatassessestheimportanceoffieldmarginsforbirdpopulations indifferentfarmlandsofCEE. Theunder-representationof such informationinrecentliteraturealsostemsfromthefactthatmany modernlandscapeassessmentsuseremotesensingdatawhichlack ofdetail(Hazeuetal.,2014;Kosicki&Chylarecki,2012).Fine-scale linearlandscapeelements(hedgerows,foreststrips,livefences, drainageditches,littlestreams,roads,verges,footpaths,(Höbinger, Schindler,Seaman,Wrbka,&Weissenhofer,2012))andotherkey microhabitatsareoverseenininputdatasets,limitingtheaccuracy ofconclusions.

Toassessthestateandhabitatassociationsoffarmlandbirds, researchoncommunitieshasprincipallyfocusedeitheronbroad scale assessments or on small-scale habitat studies. Studies at anintermediatespatialscaleemploying sampleplotsof several dozenhaarefarlesscommon(e.g.Heikkinen,Luoto,Virkkala,&

Rainio,2004).Thisscale allowstheﬁeld worktobeconducted withaccuracy(e.g.,usinglaboriousbutreliablemappingmethods) and tocountallspecieswithin thesurveyedareas.Asa result, there in a noticeable lack of recent studies in CEE comprising wholebird communities;most studiesconcentrate onselected speciesorecological/taxonomicgroups.Tryjanowskietal.(2009) reviewedthePolishliteratureonavianecologyandfoundmerely

11 qualitystudies assessingthecomplete bird communities on soundagriculturallandscapeplots(>3km²).

Theaims ofthis paperweretoassess:(1) bird speciesrich- nessandabundanceincontrastingagriculturallandscapesofSW Poland,(2)numberofbirdspecies,breedingdensityandcommu- nitycompositioninresponsetotheaggregationofdifferentﬁeld margintypesand,(3)theinputoffourmajorhabitatsinthestudied landscapestothewholebirdcommunityandthemostnumerous species,includingtheshareofpairsbreedinginﬁeldmargins.

2. Methods 2.1. Studyarea

The study was conductedin diverseagricultural landscapes of the Lower Silesia region covering the SW corner of Poland.

Theregionisnothomogeneousregardingagriculturallandscapes andfarmingintensity.Generally,farmingintheLowerSilesiais moreintensivethaninEasternPoland(thatoftenresembletradi- tionalfarmlands),butnotasmuchasinsomeWesternEuropean countries.Theintensificationprocessesareclearlyvisibleinparts oftheregion,butmanycharacteristicsoflow-intensityfarmingstill retainedintheotherparts.SWPolandrepresentstypicalCentral- Europeanlandscape, which hasbeen confirmedby comparable valuesofindicatorsofland-useandagriculturalproduction(see Wuczy ńskietal.,2014).Theseregionalfeaturesallowedacom- parative between-landscape study to beconducted within one geographicalunit.

2.1.1. Landscapeplots

Twelvestudyplotsofca.50haeach(603.2ha).Threecontrasting groupsofplotswereselectedtoreﬂecttheprevailingtypesofmod- ernarablefarmlandinPoland,andmoregenerallyinCEE(Fig.1, Table1,AppendixA):

Shrubbymosaicplots:Coveredbysmall,privately-ownedfields (0.1haupto8.6ha),afewmid-fieldwoodlotsandafewperma- nentfallows,andanetworkoflinear,semi-naturalfieldmargins (describedbelow).Theseheterogeneousplotsreflectedamodelof traditional,low-intensityfarming,whichisdisappearinginEurope butstillexistsinsomePolishlandscapes.Accordingtorecentter- minologyappliedtoagriculturallandscapes,shrubbymosaicplots matchthe“HighNatureValueFarmlandType2”(i.e.,“farmland withamosaicoflowintensityagricultureandnaturalandstruc- tural elements, suchas field margins,hedgerows, stone walls, patches ofwoodland or scrub,small rivers”(Paracchini, Terres, Petersen,&Hoogeveen,2007)).

Openmosaicplots:Similartotheshrubbymosaicplotsaccording toownership,land-useandﬁeldsizes,butalmostlackingofhigh vegetation.Openmosaicsarecommonespeciallyinlowlandsof centralandeasternPoland.

Openplainplots:Intensivelyused,coveredbyafewlargearable ﬁeldsand,consequently,withaverylowaggregationofﬁeldmar- ginsandalmostdevoidofothernon-croppedhabitats.Thistype offarmlandisrapidlyincreasingafterEUaccession,especiallyin westernPoland.

It is noteworthythat theopen mosaicand open plainplots werecombinedinsomeanalyzes.Eachplotwasdigitallymapped usingGIS,allowingforfurtherspatialanalyzes.Altogether,crop- land(including2.2%ofgrasslands)constituted91.1%ofthearea, followedby4.4%permanentfallows(coveredbyperennialvegeta- tion),4.0%ﬁeldmargins,0.4%mid-ﬁeldcopses;meanarea0.36ha, range0.03–0.96ha,N=7;Fig.1).Themaincropswerewinter-and spring-sowncereals(ratio–ca4:1,respectively,mainlywheat,barley,rye),oilseedrape,maize,androotplants(e.g.,potatoes,sugar beets).Fallows,copses,andgrasslandsoccurredalmostexclusively

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Fig.1. DistributionofstudyplotsagainstthemapofSWPoland,andtheoutlinesofexampleshrubbymosaic(JAZ),openmosaic(KMO),andopenplain(FUN)plots.Crops andotherlandcovertypesareshownbydifferentcolors(i.e.,red–permanentfieldmargins,green–wintercereals,greyandorange–springcereals,yellow–winterrape, pink–sugarbeet,brown–potato,celadon-maize,beige–fallow).Fordetailedlocationsofthestudyplots,thereaderisreferredtotheGoogleEarthfileinthewebversionof thearticle.(Forinterpretationofthereferencestocolorinthisfigurelegend,thereaderisreferredtothewebversionofthisarticle.)

intheshrubbymosaicplots.Thenumberofmaturetrees(≥30cm diameteratbreastheight)wasalsocountedtorepresenttheoccur- renceofwoodyplantsineachstudyplot,andtotallyamountedto 435trees,mostlyofdeciduousspecies.

2.1.2. Fieldmargins

Specialattentionwasdevotedtofieldmarginsfortheircom- monoccurrenceinfarminglandscapesandresultingimportance forbiodiversity.Inthisstudy,edgesofallseparatedfields,result- ingfromthecurrentland-use,wereconsideredasfieldmargins.No marginstripsmanagedforconservation,whichwerecomponents ofagri-environmentschemesinEU(Vickery,Feber,&Fuller,2009), occurredinthestudiedagriculturallandscape.Threenotexclusive typesofmarginsweredistinguishedtodeterminetheirrelationship withbirddiversity:

Allfieldmargins:Allboundariesofseparatedfieldpatches,both seasonalandpermanent,wellreflectingtheland-usecomplexity.

Permanentﬁeldmargins:Semi-naturalhabitatsusuallyassoci- atedwithhuman-madelandscapefeatures(roadsandditches),and coveredwithalushspontaneousvegetation.

Shrubbyfieldmargins:Subsetoftheformer group,limitedto stretcheswithshrubsandisolatedtrees,includingremnantsoffruit treelinesandfieldedgesadjacenttomid-fieldwoodlotsandforests adjoiningthestudyplots.

Theauthoralsocharacterizedthemarginsintermsoftheirveg- etationstructure,lengthsandwidths,usingGeoMediaProfessional 5.2GISsoftware(http://www.intergraph.com).

2.2. Fieldprocedures

Birdsweresurveyedusingthespot(territory)mappingmethod (Ralph,Geupel,Pyle,Martin,&DeSante,1993;Sutherland,2006) inthreebreedingseasons:theshrubbymosaicplotswereinvesti- gatedin2004and2005,whereastheopenmosaicandopenplain plotsin2007.Despitedifferentyearsofcounting,birddatacould becomparedamongplotsthankstocontrastingdifferencesinhabi- tatcharacteristicsbetweenthetwoplotgroups(shrubbyvsopen) andminorbetween-yeardifferencesinshrubbymosaicplots(see below).Prior tocounts,detailed maps of each studyplotwere generated.Land-usewasfurthervalidatedintheﬁeld.Allﬁeldbor- dersandsomelandscapefeatures,suchassemi-naturalhabitats

Table1

Plottraitsdividedintogroups(representingvarioustypesoflandscapes).

Plot Landscape Area(ha) Aggregation^aofﬁeldmargins[km/km²] No.oftrees

Allmargins Permanentmargins Shrubbymargins

1SIE Shrubbymosaic 50.8 24.4 13.8 3.9 10

2SIW Shrubbymosaic 50.7 23.6 14.7 4.8 30

3JAZ Shrubbymosaic 49.0 26.6 11.2 6.4 54

4SLU Shrubbymosaic 52.6 30.9 12.3 8.0 112

5WIS Shrubbymosaic 48.1 24.1 14.2 9.3 134

6WIN Shrubbymosaic 52.9 25.0 16.5 4.3 91

7KMO Openmosaic 49.7 19.8 5.6 0.4 0

8KLU Openmosaic 50.0 17.7 3.6 0.3 1

9KUN Openmosaic 49.1 18.7 6.4 0.0 0

10FMO Openplain 50.1 2.9 1.2 0.0 0

11FLU Openplain 50.1 3.1 3.1 0.0 0

12FUN Openplain 50.2 4.2 0.7 0.1 3

Shrubbymosaic(mean±SD) 50.7±1.9 25.8±2.7 13.7±1.9 6.1±2.2 71.8±48.4

Open(mean±SD) 49.8±0.4 11.1±8.5 3.4±2.3 0.1±0.2 0.7±1.2

Openmosaic(mean±SD) 49.6±0.4 18.8±1.1 5.2±1.5 0.2±0.2 0.3±0.6

Openplain(mean±SD) 50.1±0.1 3.4±0.7 1.7±1.3 0.0±0.0 1.0±1.7

Allplots(mean±SD) 50.3±1.4 18.4±9.7 8.6±5.7 3.1±3.5 36.3±49.5

aNotethattheterm‘aggregation’isidenticalwiththe‘density’ofﬁeldmargins;thelattertermisrarelyusedinthispapertoavoidconfusingwiththedensityofbirds.

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(patchesoffallows,isolatedtreesorshrubs),andpowerlines,were includedinthemaps.Thiswassufﬁcientforprecisebirdmapping intheshrubbyandopenmosaicplots.Toenhancebirdmapping inthethreeopenplainplots,thesecomponentswereadditionally markedinagridof150m×150m.

AllpartsofeachstudyplotwerevisitedbetweenAprilandJuly onﬁveoccasions;fourinthemorningandoneintheevening,under appropriate weather conditions (norain, fogand strongwind).

Themorningcounts beganaroundsunrise andwerecompleted by10:00a.m.CET;somecountswereextendeduntilnoonwhen nestswereidentiﬁedandcontrolled.Theeveningvisitwasdone for censusingmainly dusk-active birds, including thePartridge (Perdix perdix),Common Quail (Coturnixcoturnix), Grasshopper Warbler(Locustellanaevia),Blackbird(Turdus merula) (Cramp &

Simmons,2004).Standardconventionsoftheterritorymapping methodwere used torecord bird activities (Sutherland, 2006).

Thepositionsoftherecordedbirdsweremarkedonamapusing standardcodes.Carewastakentorecordsimultaneousterritorial behaviorandanyotherindicationsofbreeding(e.g.,foundnests, social behaviors, birds carrying food, nesting materials). When countingSkylarks,thesitesoftakingoffandlandingafterasong- flightweremappedtoestimatetheterritories.Intheterritories assignedduringthecounts,nestsoftwofieldmarginspecialists, theRed-backedShrike(Laniuscollurio)andBarredwarbler(Sylvia nisoria)wereactivelysearchedforandmappedforanotherproject (Orłowski,Wuczy ński, &Karg,2015).Thenumber ofterritories andhabitatassociationsoftheMarshHarrier(Circusaeruginosus) wereestablishedbasedonregular(duringeachcount)observations ofadultbirdsandtheirsocialbehaviors(e.g.,between-neighbors fights,courtship, carrying giftsfor a mate)(Cramp &Simmons, 2004).

2.3. Quantifyingabundanceofbirds

Aftereachbreedingseason,recordsweremapped.Territories wereassignedinrelationtothedistributionofclustersofsightings.

At least two registrations were taken as evidence of a partic- ularterritory, exceptionallyit was oneregistration–in the case ofcertainevidenceofbreeding(nests)orsomelatemigrantsof irregularsongactivity,suchastheMarshWarbler(Acrocephalus palustris).Inthecaseoftheedgeclusters,thosethatoverlapthe plotboundary,halfoftheterritorywascountedasbelongingto theplot.Territorieswerethen countedtocalculatethepopula- tionmetricsusedinfurtheranalyzes:(1)species richness:sum of species havingany territory within the plot, (2) number of breedingpairs: sumof territoriesof each bird species, and (3) density:numberofbreedingpairsper10ha.TheCuckoo(Cucu- luscanorus)wasaccountedforinthenumberofspeciesbutnot inthenumberofbreedingpairsandassociatedanalyzes,because ofitsunusualbreedingsystem.Fortheshrubbymosaicplots,the mean number of speciesand breedingpairs in 2004and 2005 wascalculatedandusedinfurtheranalyzes,includingcomparisons withtheopenplots.Usingthemeanswasjustiﬁed,sincethebird indiceswereverysimilarinbothseasons,especiallythetotalnum- berofbreedingpairsinparticularplotscoincided.So,therewas nosigniﬁcantdifferencebetweenthemediannumberofspecies inbothyears(23.0and24.5,respectively,n=6,T=5.00,P=0.249) nor in the total number of breeding pairs (115.3 and 119.0, respectively,n=6,T=5.50,P=0.294;Wilcoxontest formatched pairs).

Maps of bird distributions and percentages of habitattypes (seeabove)werealsousedtoanalyzebird-habitatassociations.

Eachterritorywasassignedtooneofthefourhabitattypes:crop- fields,permanentfallows,fieldmargins,andmid-fieldwoodlots.

Usuallythe assignmentclearly arose fromclustersof sightings beinglocatedwithintheparticularhabitat.Indoubtfulsituations

halvesofterritorieswereallocatedbetweentwoneighboringhabi- tats.Thedatawereanalyzedincludingthetotalbirdcommunity andseparately,thefunctionalgroupofopenﬁeldspeciesandthe Skylark–forparticularimportanceofthesebirdsinthestudyplots andfarminglandscapesingeneral.Thespecieswereassignedto thegroupbasedontheirhabitatpreferences(Tryjanowskietal., 2009;Wuczy ´nski,Kujawa,Dajdok,&Grzesiak,2011)andindicated (Table2).

2.4. Dataanalysis

Groups ofsample plots(shrubby mosaic, openmosaic, open plain) were contrasted using bird population indices, deﬁned above,andtwodiversitymetrics:thereciprocalSimpson’sindex (D_Simpson=1/

pi2 wherepiis theproportionof pairsintheith species)andSimpson’sevennessindex(E_Simpson=D_Simpson/number ofspecies).TheauthorusedSimpson’sindex,andtheassociated evennessmeasure,becauseitisconsideredtoberobust,easyto interpret,andapplicableatsmallsamplesizes(Magurran,2004).

Moreover,E_Simpson isusefulwhenstudyareasofdifferingnum- bersofspeciesaretobecompared,becausetheindexisinsensitive to species richness. Due tosmall sample sizes, non-parametric testswereapplied:theMann–WhitneyUtestwasusedtocom- parebetween-plotdifferencesinbirdmetrics,andSpearmanrank correlationswereusedtorelatebirdabundancestomarginaggre- gations.ThecalculationsoftheUtestsandrankcorrelationswere performedwiththeSTATISTICA10package.

To examine the patterns of bird species distribution within thesampleplotsandtherelationshipwiththeﬁeldmarginsnet- work,theordinationmethodswereemployedusingCANOCOfor Windows4.5(Lepˇs& ˇSmilauer,2003).Detrendedcorrespondence analysis(DCA)wasruna priori,inordertoestimatethelength ofthecompositionalgradient.Theresultantgradientlength(e.g., 2.354fortheﬁrstaxis)indicatedthatthelinearmodelsofPCAand RDAwereappropriate(terBraak& ˇSmilauer,2002).

Principalcomponentanalysis(PCA)wasemployedtoexamine thepatternsofbirdspeciesdistributioninthethreegroupsofsam- pleplots.Theresultswerevisualizedintheordinationdiagramin CanocoDraw4.0(terBraak& ˇSmilauer,2002).Tomaketheinter- pretationofdiagrameasier,scalingofordinationscoresfocused oninter-speciescorrelationsandspeciesscoresweredividedby theirstandarddeviation.Moreover,defaultoption“centeringby species”waschosen.AlongwiththePCA,theclusteranalysiswas performedtocomparetheplotsinrelationtothesimilarityinthe compositionoftheaviancommunity.PairwiseMorisita’ssimilarity indices(Magurran&McGill,2011)forbirdabundancedatawere calculatedand displayedasa dendrogram.Clustering algorithm wastheunweightedpairgroupmethodusingarithmeticaverages (UPGMA). Thesoftware PAST3.01 (http://folk.uio.no/ohammer/

past)wasusedforclusteranalysis.

Multivariate constrained ordination redundancy analysis method(RDA)wasappliedtorelatethebirdcommunitycomposi- tiontofourexplanatoryvariables(i.e.,theaggregationsofthethree ﬁeldmargintypesandthenumberofmaturetreeswithintheplot).

Birdabundanceswerelog-transformed;centeringwasbyspecies only.TheRDAswereusedfirsttosummarizethejointeffectofthe explanatoryvariablesonbirdspeciescomposition.GlobalMonte Carlopermutationtestsofthefirstordinationaxisandthatofall canonicalaxestogetherunderthefullmodel(499permutations) testedthesignificanceofthemodel.SecondrunofRDAstested thesignificanceof individualvariables separatelyand usingthe forward selection procedure (Lepˇs & ˇSmilauer,2003). Separate testingallowedtoinspectthemarginaleffectsofallenvironmental variables onspecies composition(i.e.,theindependenteffectof the shrubby,permanent and all field margin aggregations, and thenumberoftrees).Forwardselectionrevealedtheconditional

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Table2

Birdabundancesinthethreestudiedtypesofplots.Valuesdenotethemean(±SDandrange)numberofpairsbreedingintherespectiveplottypes,thetotalnumberofpairs, andtotaldensity.Theopenﬁeldspeciesaremarkedwiththeasterisks.

Species Shrubbymosaic Openmosaic Openplain Total Density

(pairs/10ha) Mean±SD Min-Max Mean±SD Min-Max Mean±SD Min-Max

SkylarkAlaudaarvensis* 26.0±8.5 17.0–39.8 50.8±6.6 47.0–58.5 41.5±3.1 38.0–44.0 433.0 7.18

YellowhammerEmberizacitrinella 21.0±3.6 14.5–24.8 0.3±0.6 0.0–1.0 0.0 0.0 127.3 2.11

MarshWarblerAcrocephaluspalustris* 11.8±7.7 2.0–25.0 3.3±4.2 0.0–8.0 0.7±1.2 0.0–2.0 83.0 1.38 YellowWagtailMotacillaﬂava* 1.2±1.0 0.0-2.5 9.5±3.9 7.0–14.0 11.7±13.3 3.0–27.0 70.8 1.17

Red-backedShrikeLaniuscollurio 9.0±2.2 6.3–12.5 0.0 0.0 0.0 0.0 53.8 0.89

BlackbirdTurdusmerula 6.7±2.2 4.0–9.0 0.0 0.0 0.0 0.0 40.0 0.66

WhitethroatSylviacommunis 6.2±1.4 4.5–8.0 0.0 0.0 0.3±0.6 0.0–1.0 38.0 0.63

CornBuntingEmberizacalandra* 3.6±2.1 0.0–6.3 1.2±1.0 0.0–2.0 0.5±0.5 0.0–1.0 26.5 0.44

SongThrushTurdusphilomelos 4.3±2.5 2.0–8.5 0.0 0.0 0.0 0.0 25.5 0.42

WhinchatSaxicolarubetra* 3.3±2.8 0.0–6.5 0.0 0.0 0.3±0.6 0.0–1.0 21.0 0.35

BlackcapSylviaatricapilla 3.0±3.2 0.0–7.0 0.0 0.0 0.0 0.0 17.8 0.29

BarredWarblerSylvianisoria 2.8±1.2 1.3–4.3 0.3±0.6 0.0–1.0 0.0 0.0 17.5 0.29

QuailCoturnixcoturnix* 0.5±0.7 0.0–1.8 1.2±0.8 0.5–2.0 3.0±1.8 1.5–5.0 15.8 0.26

GreenﬁnchCarduelischloris 2.0±1.6 0.0–4.0 0.0 0.0 0.0 0.0 12.3 0.20

PheasantPhasianuscolchicus 1.9±1.7 0.0–4.8 0.0 0.0 0.0 0.0 11.3 0.19

ChafﬁnchFringillacoelebs 1.9±1.9 0.0–4.3 0.0 0.0 0.0 0.0 11.3 0.19

TreeSparrowPassermontanus 1.6±1.3 0.0–3.8 0.0 0.0 0.0 0.0 9.5 0.16

LinnetCardueliscannabina 1.3±1.1 0.0–2.8 0.0 0.0 0.0 0.0 7.8 0.13

ReedBuntingEmberizaschoeniclus 1.1±1.2 0.0–3.3 0.3±0.6 0.0–1.0 0.0 0.0 7.8 0.13

StonechatSaxicolarubicola* 1.0±0.9 0.0–2.0 0.3±0.6 0.0–1.0 0.0 0.0 7.0 0.12

GreyPartridgePerdixperdix* 0.2±0.3 0.0–0.5 1.0±1.0 0.0–2.0 1.0±1.0 0.0–2.0 7.0 0.12

BlueTitCyanistescaeruleus 1.2±1.0 0.0–2.8 0.0 0.0 0.0 0.0 7.0 0.12

HawﬁnchCoccothraustescoccothraustes 1.1±0.9 0.0–2.5 0.0 0.0 0.0 0.0 6.8 0.11

MarshHarrierCircusaeruginosus 0.0 0.0 1.2±0.6 0.5–1.5 0.8±0.3 0.5–1.0 6.0 0.10

GardenWarblerSylviaborin 1.0±2.1 0.0–5.3 0.0 0.0 0.0 0.0 5.8 0.10

StarlingSturnusvulgaris 0.8±0.8 0.0–2.0 0.2±0.3 0.0–0.5 0.0 0.0 5.3 0.09

GrasshopperWarblerLocustellanaevia* 0.8±0.8 0.0–2.0 0.0 0.0 0.0 0.0 4.5 0.07

GreatTitParusmajor 0.7±0.7 0.0–1.8 0.0 0.0 0.0 0.0 4.3 0.07

ChiffchaffPhylloscopuscollybita 0.7±0.7 0.0–2.0 0.0 0.0 0.0 0.0 4.3 0.07

LesserWhitethroatSylviacurruca 0.6±0.7 0.0–1.8 0.0 0.0 0.0 0.0 3.8 0.06

GoldﬁnchCardueliscarduelis 0.6±0.7 0.0–1.8 0.0 0.0 0.0 0.0 3.5 0.06

SerinSerinusserinus 0.5±0.8 0.0–2.0 0.0 0.0 0.0 0.0 2.8 0.05

DunnockPrunellamodularis 0.4±0.7 0.0–1.5 0.0 0.0 0.0 0.0 2.5 0.04

GreatSpottedWoodpeckerDendrocopos major

0.4±0.4 0.0–1.0 0.0 0.0 0.0 0.0 2.3 0.04

IcterineWarblerHippolaisicterina 0.3±0.8 0.0–2.0 0.0 0.0 0.0 0.0 2.0 0.03

LapwingVanellusvanellus* 0.1±0.3 0.0–0.8 0.3±0.6 0.0–1.0 0.0 0.0 1.8 0.03

RiverWarblerLocustellaﬂuviatilis 0.3±0.4 0.0–1.0 0.0 0.0 0.0 0.0 1.8 0.03

TurtleDoveStreptopeliaturtur 0.3±0.4 0.0–1.0 0.0 0.0 0.0 0.0 1.5 0.02

WoodpigeonColumbapalumbus 0.2±0.5 0.0–1.3 0.0 0.0 0.0 0.0 1.3 0.02

GreatGreyShrikeLaniusexcubitor 0.2±0.3 0.0–0.8 0.0 0.0 0.0 0.0 1.3 0.02

GoldenOrioleOriolusoriolus 0.2±0.2 0.0–0.5 0.0 0.0 0.0 0.0 1.3 0.02

PiedWagtailMotacillaalba 0.1±0.2 0.0–0.5 0.0 0.0 0.2±0.3 0.0–0.5 1.0 0.02

GreatReedWarblerAcrocephalus arundinaceus

0.2±0.3 0.0–0.5 0.0 0.0 0.0 0.0 1.0 0.02

WryneckJynxtorquilla 0.1±0.2 0.0–0.5 0.0 0.0 0.0 0.0 0.8 0.01

CollaredDoveStreptopeliadecaocto 0.1±0.2 0.0–0.5 0.0 0.0 0.0 0.0 0.8 0.01

MallardAnasplatyrhynchos 0.1±0.2 0.0–0.5 0.0 0.0 0.0 0.0 0.5 0.01

FieldfareTurduspilaris 0.1±0.2 0.0–0.5 0.0 0.0 0.0 0.0 0.5 0.01

SpottedFlycatcherMuscicapastriata 0.1±0.2 0.0–0.5 0.0 0.0 0.0 0.0 0.5 0.01

NightingaleLusciniamegarhynchos 0.1±0.2 0.0–0.5 0.0 0.0 0.0 0.0 0.5 0.01

CuckooCuculuscanorus + +

Totalnoofpairs 121.4±19.6 95.8–154 70.0±9.3 63.0–80.5 60.0±14.8 50.5–77.0 1118.3

Density(pairs/10ha) 23.9±3.2 19.5–29.3 14.1±1.8 12.7–16.1 12.0±3.0 10.1–15.4 18.54

effects(i.e.,theeffectthateachvariablebringsinadditiontoall thevariablesalreadyselected).Asbefore,thesigniﬁcanceofthe relationshipsbetweentheenvironmentalvariablesand thebird communitiesweredeterminedusingMonteCarlotestwith499 unrestrictedpermutations.

Finally,IusedPASTtochecktheeffects oftheproportionof fourhabitattypes(fieldmargins,copses,fallows,andcropfields) onbirdabundance.Theeffectsweretestedwitharandomization testofgoodness-of-fit,with9999randomreplicates.Thetest is analternativetothemorepopularchi-squaretest,whenthesam- plesizesaresmall(Sokal&Rohlf,1995).Sincethepercentagesof threehabitats(exceptcropland)weresmall,thederivedexpected birdcountvalueswerealsosmallandtherandomizationtestwas appropriate.

3. Results

3.1. Between-plotdifferencesinbirdabundances

Atotalof50birdspeciesbreedinginameandensityof18.5 pairs/10ha(SD±6.3)wererecordedinthe12studyplots(Table2, AppendixB).Pronouncedbetween-plotdifferenceswereobserved regardingboththenumberofspeciesandbreedingpairs(tenand three-foldmin-maxdifferences,respectively;Table2).Therewas ahighly signiﬁcantdifferencebetweentheshrubbymosaic and openlandscapesregardingspeciesrichness,birdnumbersandden- sity,andspeciesdiversity(P<0.01ineachcase),butnotspecies evenness (Table 3).Generally the indices of bird communities werearrangedalongadecreasinggradientofstudysites:shrubby

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Table3

Indicesoftotalbirdcommunities,openfarmlandspecies,andtheSkylarkinthestudyplots.Meanvaluesareshown(min-maxinparentheses).

Variable Shrubbymosaic

plots(n=6)

Openplots(n=6) P^a Openmosaicplots (n=3)

Openplainplots (n=3)

P^a Allplots(n=12)

Numberofspecies 45(20–36) 16(4–9) <0.01 13(6–9) 10(4–9) 0.64 50(4–36)

Numberofbreedingpairs 728.3(95.8–154.0) 390(50.5–80.5) <0.01 210(63.0–80.5) 180(50.5–77.0) 0.38 1118.3(50.5–154.0) Totaldensity(pairs10ha⁻¹) 23.9(19.5–29.3) 13.0(10.1–16.1) <0.01 14.1(12.7–16.1) 12.0(10.1–15.4) 0.38 18.5(10.1–29.3) Indexofdiversity(DSimpson) 9.78(6.21–14.61) 1.87(1.31–2.31) <0.01 1.82(1.74–1.90) 1.92(1.31–2.31) 1.00 5.55(1.31–14.61) Evennessindex(ESimpson) 0.20(0.28–0.35) 0.12(0.19–0.33) 0.30 0.14(0.19–0.32) 0.19(0.21–0.33) 0.19 0.11(0.19–0.35) Shareofopenfarmlandspecies

(%ofbreedingpairs)

40.0(19.5–61.3) 97.2(97.5–98.7) <0.01 96.7(95.7–98.4) 97.8(96.2–98.7) 0.66 59.9(19.5–98.7)

Densityofopenfarmland species(pairs10ha⁻¹)

9.6(4.8–14.0) 12.7(9.9–15.4) 0.13 13.6(12.5–15.4) 11.7(9.9–15.2) 0.38 11.1(4.8–15.4)

DensityofSkylark(pairs 10ha⁻¹)

5.1(3.5–7.8) 9.3(7.6–11.7) <0.01 10.2(9.5–11.7) 8.3(7.6–8.8) 0.08 7.2(3.5–11.7)

aThesigniﬁcancelevelwastestedwithMann–WhitneyUtest.

mosaic–openmosaic–open plain.Highervalues in species rich- nessandbirdabundancewerenotedintheopenmosaicthanin openplainplots(13and10species;14.1and12.0pairs10ha^–1, respectively),butthedifferenceswerenotsigniﬁcant.

Thegroupoftenopenfarmlandspeciespredominatedinbird communities,reachingupto98.7%ofbreedingpairsinopenplain plots.Thegrouphadhigher,yetnon-significantdensitiesinopen landscapescomparedtoshrubbymosaicplots(Mann–WhitneyU test:Z=–1.52,P=0.13),andinopenmosaicthanopenplainplots (Z=–0.87,P=0.38)(Table3).Thispatternwascreatedmainlybythe Skylarks,themostnumerousofthetruefarmlandspeciesandofthe wholebirdcommunity(38.7%ofthetotalbreedingpairs).Themean densityofSkylarkwassignificantlyhigherinopenthaninshrubby mosaic plots (Z=–2.64,P=0.008);thedifferencebetween open mosaicandopenplainplotswasmarginallysignificant(Z=–1.75, P=0.08),withhighervaluesintheformergroup.

Thenumberofspeciesandbreedingpairswerehighlycorrelated withtheaggregationofﬁeldmargins,andthecorrelationstrength has apparently been weakly related to the subset of margins taken(all,permanentorshrubbymargins)(Table4).However,the inspectionofscatterplots(AppendixC)indicatedthattheobserved relationshipswerecreatedmainlybythedifferencebetweenthe groupsof shrubbymosaicand openplots.Whenlimited tothe sub-sampleofopenplotstherelationshipswereweak.

3.2. Birdcommunitiesamongthestudyplots

PCAordinationresultsconﬁrmedthatthethreegroupsofsam- plesiteswereinhabitedbypartlydifferentbirdcommunities.The ﬁrstPCAaxisexplainedmost(75.2%)ofthetotalspeciesvariance andclearlyseparatedtheshrubbymosaicplotsfromtheopenplots.

Theeigenvalueforaxisonewas0.75andforaxistwo0.10.Thus, thefirstaxiscanbeidentifiedwiththegradientofthehighvege- tationcover,withtypicalopenfarmlandspecies(Skylark,Yellow Wagtail-Motacillaflava,orin-fieldbreedingMarshHarrier)related totheopenplotsintherightsiteofthediagram,andallthespecies connectedwithforestandmixedhabitats–ontheleftsite(Fig.2).

ThesecondPCAaxis(10.3%oftheexplainedvariance)reﬂectsland- usepatternsandﬁeldcomplexity.Thegroupofspecies,suchas

theReedBunting(Emberizaschoeniclus),MarshWarbler,Stonechat (Saxicolarubicola),andtheCornBuntingE.calandra,tendstohave largerabundanceinmosaicsampleplotswithalotoffallowland, whereasYellow Wagtail,Quail,and surprisinglyPartridge,were linkedtouniform,intensivelyusedagrocenoses.

Clusteranalysisconﬁrmedthatbirdcommunitiesclearlydif- feredinshrubbymosaicvsopenplots;bothgroupscreatedseparate clusters in the dendrogram produced by the analysis (Fig. 3).

Within-clusterdifferentiationwaslessexpressed,speciﬁcallythe compositionaldifferentiationbetweenopenmosaicandopenplain plotswasnotobserved.Thismightbeduetothefactthattherela- tivelyrarespecieshavelittleeffectontheMorisitaindex.Overall, similarandhighvaluesoftheindexassociatedwithopenplotsindi- catedthatopenlandscapeswereinhabitedbybirdcommunitiesof similarstructure.Relativelydistantpositionof10FMOreﬂected particularlyhighdensityofYellowWagtailandQuailinthissite (AppendixB).In shrubbymosaicsthesubgroupof6WINand1 SIEwasrelatedtohighnumbersofseveralopenfarmlandspecies, includingSkylark,inbothplots.

Redundancyanalysisillustratedtheimportanceofvariousﬁeld marginsandmaturetreesforthestructureofthebirdcommunity.

Asetoffourenvironmentalvariablesweresignificantlyrelatedto thespeciesdata;boththetestonthefirstaxis(F=14.29,P=0.002) andthetestonallcanonicalaxes(F=7.39,P=0.002)werehighly significantunderfullmodel.Thevarianceofspeciesdataaccounted forbythefirsttwoaxeswas75.6%(eigenvalues0.671+0.085)of thetotal variation inthe bird community, which suggeststhat theselectedenvironmentalvariablesarethoseresponsibleforthe variationinspeciescomposition.Astepwiseprocedureallowedto directlyextractthevariationthatisexplainablebythemeasured characteristicsoffieldmarginsandtreenumbers.Separatetesting revealedthesignificantinfluenceoftheshrubby,permanentand allfieldmarginaggregations,andthenumberoftrees(P<0.01in eachcase,Table5).However,usingtheforwardselectionproce- dureonlytwovariablesweresignificant–theaggregationsofthe shrubby(P=0.002)and permanent(P=0.006)margins.Interest- ingly,thenumberoftreesdidnotsignificantlyincreasethefitof themodel(P=0.06)suggestingthatthenetworkofwell-vegetated fieldmarginsissufficientinexplainingthebirdcommunities.The

Table4

Spearmancorrelationcoefficients(rs)relatingtheaggregationsoffieldmarginsandbirdindicesinthe12studyplots.Separatecorrelationswereperformedfortheaggregation ofall,permanentandshrubbyfieldmarginsagainstthenumberofbirdspeciesandnumberofbreedingpairs.Thescatterplotsillustratingtheserelationshipsarepresented inAppendixC.

Aggregationofﬁeldmargins(km/km²) N Numberofspecies Numberofbreedingpairs

rs P rs P

AllFM 12 0.820 0.001 0.811 0.001

PermanentFM 12 0.742 0.006 0.818 0.001

ShrubbyFM 12 0.957 <0.001 0.803 0.002

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Fig.2.PCAordinationresultsshowingdifferencesinbreedingbirdcommunitiesbetweentheshrubbymosaic(red),openmosaic(gray),andopenplain(yellow)plots enclosedinpolygons.TheplotsarelabeledasinTable1.SpeciesarerepresentedbyabbreviationsoftheirLatinnames.Forclarity,onlyspeciesthathavemorethan30%of theirvariabilityexplainedbythefirsttwoaxesaredisplayed.Thefirsttwoaxesexplain85.6%(eigenvalues0.752+0.104)ofthetotalvariationinthebirdcommunity.(For interpretationofthereferencestocolorinthisfigurelegend,thereaderisreferredtothewebversionofthisarticle.)

discrepancybetweenthemarginalandconditionaleffects(Table5) iscausedbythemutualpositivecorrelationsbetweentheaggrega- tionsofvariousﬁeldmarginsandtreenumbers.

3.3. Theresponseofbirdabundancetotheproportional availabilityofhabitats

Therewasasignificantrelationshipbetweentherelativeareaof fourhabitattypesonbirdabundancewithaparticularimportance offieldmargins(Fig.4).Overall,35%ofbreedingpairswerenoted inthishabitat(coveringmerely4%ofthetotalarea),andexcluding Skylarkthisincreasedto55%.Intheshrubbymosaicplots,halfof thepairs(50.3%)werenotedinfieldmargins.Thirteenof16ofthe mostnumerousspeciesrevealedsignificantassociationswithfield

margins,andtheRed-backedShrike,Yellowhammer(Emberizacit- rinella),Blackbird,andBarredWarblermaybeconsideredmargin specialists,as more than 70%of pairs bred in this habitat.The Chaffinch(Fringillacoelebs)andBlackcap(Sylviaatricapilla)were particularlydependentonmid-fieldwoodlotsandtheWhinchat (Saxicolarubetra)wasnotedmostlyinpermanentfallows.Three truefarmlandspecies(i.e.,Quail,Skylark,YellowWagtail)bredpre- dominantlyincropfields,andtheseweretheonlyspeciesinwhich thedensityfiguresdidnotdepartfromexpected.

4. Discussion

This study analyzed the breeding bird communities in typ- ical, yet contrasting, farmland types in the central-European

Table5

Theinfluenceoftheshrubby,permanentandallfieldmargin(FM)aggregations(km/km²)andnumberofmaturetreesonbirdspeciescomposition.Summaryofthe multivariateanalysis,withthefourvariablestestedseparately(marginaleffects),andusingtheforwardselectionprocedure(conditionaleffects).Significancevaluesobtained throughMonteCarlopermutations.

Variable Marginaleffects Conditionaleffects

Explainedvariance(%) F P Explainedvariance(%) F P

ShrubbyFM 67.2 20.507 0.002 67.2 20.507 0.002

PermanentFM 57.6 13.606 0.004 9.6 3.712 0.006

No.oftrees 54.2 11.829 0.002 1.7 0.604 0.718

AllFM 42.2 7.294 0.006 1.5 0.546 0.756

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Fig.3.Dendrogramofclusteranalysis(UPGMA)usingMorisitasimilarityindex forthebirdcommunitiesoftheinvestigatedstudyplots.Theshorterconnections betweentwoplotsinthediagram,themoresimilartheplotsare.Codesoftheplots deﬁnedinTable1:1–6–shrubbymosaic,7–9–openmosaic,10–12–openplainplots.

countrysideshortlyafterEUaccession.Studysitesdifferedwiththe farmingregimesexpressedbytheaggregationoffieldmargins–a distinctlandscapefeatureofPoland.Notsurprisingly,therewere significantdifferencesbetweenfarmlandtypesinspeciesrichness, diversity and densities of birds.An averagenumber of species wasfour-foldhigherinshrubbymosaicthaninopenplots,index ofdiversity wasfive-fold higher and birddensity wastwiceas high.Congruentwithresultsofthisstudy,apositiverelationship betweenspeciesrichnessandfarmlanddiversificationhavebeen

foundinmanyotherplantandanimaltaxa(e.g.Fahrigetal.,2015).

Incontrasttotheabovemetrics,themeasureofevennesswasnot associatedwiththestudiedfarmlandtypes.SinceE_Simpson reﬂex differencesintheabundancesofthespecieswithincommunities andisnotsensitivetospeciesrichness,itcanbeassumedthateven inthemostdiversefarmlandsbird communitiesaredominated byafewspeciesofveryhighabundance,virtuallyopenfarmland species. These results also suggest that differences in species diversityaredrivenbydifferencesinthenumberofspecies,rather thantheevennesscomponentoftheindex.

Surprisingly,theauthorfounddifferencesbetweenresultsof this studyand analogous studiesin theabundanceof breeding birds;regardlessoffarmlandtypes,theobtaineddensitieswere usuallymuchhigherinthisstudy.Inthe11Polishfarmlandbird studiesconductedinareasvaryinginhabitatstructureandman- agementintensity,theweightedmeandensityamountedto9.5 pairs/10ha(range:4.5–15.1)(Tryjanowskietal.,2009),whichis substantially less thanin this study.In addition,the densityof thedominantspecies,Skylark, whichinthis studyaveraged7.2 pairs/10ha,wasamongthehighestdensitiesrecordedinPoland, and substantially exceededmostof thewesternEuropeandata (Kragten,Trimbos,&deSnoo,2008;Rahman,Tarrant,McCollin,

&Ollerton,2012).

Thesedifferencescouldarisefromregionalandlocalattributes ofthestudyplots.TheyarelocatedinthewarmestregionofPoland, withfertilegroundsandwithinarablefarminginterspersedwith fallows and a variety of non-cropped habitats. The latter were particularlyimportantfordensityfigures:well-vegetated,semi- naturallinesandpatchesdidnotsignificantlyreducethedominant fieldspecies,buthadastrongpositiveinfluenceonalargegroupof scrublandbirds(Berg,2002;Szyma ński&Antczak,2013).There- fore, my data provide evidence that agriculturallandscapes in Polandindeedsupportlargebirdpopulations,whichstillresistagri- culturalintensification.Eventhemosthomogeneousplotsthatcan beclassifiedashigh-intensityagricultureinCEE(althoughpossibly ofmedium-intensitybywesternEuropeanstandards)heldstrong populationsoffarmlandspecialists,suchasYellowWagtailorSky- lark.Ontheotherhand,lownumbersofsomespecies,suchasthe Lapwing(Vanellusvanellus)orPartridgereflectadecreasingtrend

Fig.4. Comparisonofpercentagesharesofthefourmainhabitattypeswithinthestudyplots,thetotalabundanceofthebirdcommunityandtheabundancesof16ofthe mostnumerousspecies(>10breedingpairs;seeTable2).Thespecieshavebeenarrangedaccordingtotheincreasingshareofpairsbreedinginfieldmargins.Asterisks indicatesignificantdifferencesinproportionsobtainedinarandomizationtestofgoodness-of-fit(d.f.=3):ns–notsigificant,*P<0.0001.

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intheiroverallpopulations(Kuczy ´nski&Chylarecki,2012),which mayresultfromaconsistentworseningoffarmlandquality.

Landscapecomplexityalsomoldedbirdspecies composition.

Thebird community changed from beingtotally dominated by open-farmlandspeciesinopenplainplotstobeingdominatedby speciesofﬁeld-forestmosaic,atlowproportionsofnon-cropped habitatpatches.The number of Skylarksin openplots reached 87%of breedingpairs,but inshrubbymosaic plots thespecies’

abundancewascomparableorlowerthanthatofthesecondmost numerous species, the Yellowhammer. Projection of species in thePCA ordination diagram revealed that the most numerous, ecologicallydiversecommunities wereconnectedwithshrubby mosaic plots certifying theimportance of heterogeneous landscapes. These plots also supported more species recognized as threatenedandofconservationconcerninEurope,suchastheTur- tleDove(Streptopeliaturtur),Red-backedShrike,GreatGreyShrike (Laniusexcubitor),CornBunting,TreeSparrow(Passermontanus), Linnet(Cardueliscannabina)(Skórkaetal.,2006).Thisinformation maybeimportantinconservationpractice;consideringthatsites withconditionssupportingpriorityspeciesreceivemoreattention thansitesdominatedbycommonspecies(Wuczy ´nskietal.,2014), butseeSantanaetal.(2014)whoshowedthatfocusingconserva- tioninvestmentonﬂagshipspeciesdoesnotnecessarilyfacilitate widerbiodiversity.

Openfarmland birdspecies clearlyseparated theopenplots from shrubby mosaic plots, as reveled in biplot of PCA. More interestingly,thepositionsofthesespeciesalsodisplayeda dif- ferencebetweenopenmosaic andopenplainplots, proxies for farmingintensity.Skylarksshowedanaffinitytoopenmosaicplots confirmingthatlow-intensityarableareasresemblingtraditional practicesaremorebeneficialforthisspeciesthanopenbutinten- sivelyusedfarmland(Eraud&Boutin,2002;Fischer,Jenny,&Jenni, 2009).Incontrast,theQuailwasparticularlyfrequentinthesim- plest,homogeneouslandscapes,representedbyopenplainplots.

Theseresultsareconsistentwithrecentcountrywideﬁndingsthat inPolishfarmlands,theQuaildonotprefertraditionalagriculture butareassociatedwithlargearableﬁelds(Kosicki,Chylarecki,&

Zduniak,2013).Thismaysuggest thatthis is oneof just a few speciesthatbenefitsfromcurrentchangesinmodernagriculture, althoughtheadaptive valueofsuchpreferencesisquestionable (Kosickietal.,2013),andalong-termpopulationdecreaseisalso notedinPoland(Kuczy ński&Chylarecki,2012).Surprisingly,most oftherecordedPartridgeterritories(6/7)werealsoconcentrated inopenplots,andinequalnumbersinopenplainandopenmosaic plots.Thismaybedue toahighpredationpressure inshrubby mosaicplotssuggestedbyamuchhigherdensityofdensoftheRed Fox(Vulpesvulpes),ascomparedwithopenplots(A.Wuczy ński, personalobservation)(Panek,2013;Tryjanowskietal.,2011and furtherreferencestherein). Finally,in openplotsan interesting occurrenceof theMarsh Harrierwas noted.Thisspecies is not particularlyrare in agriculturallandscapesof Poland;however, itsoccupationofterritoriesincropfieldsisarelativelynewphe- nomenon since the 1980s, which is unique to western Poland (Tomiałoj ć&Stawarczyk,2003).InSWPoland,thevastnessoffields inopenplainplotsandanotableexuberanceofcropssuchaswinter barley,wheatandrapealready,inApril,werelikelytocreatefavor- ableconditionsfortheoccurrenceoftheMarshHarrier(Cardador, Carrete,&Ma ñosa,2011).

Thelengthordensityoflinearhabitatsisfrequentlyusedasa biodiversityindicatorinfarmlands,butitsusefulnessdependson thedefinitionofhabitats,onlocallandscapecharacteristicsand onfarmingcircumstances(Billeter etal.,2008;Scozzafava&De Sanctis,2006).Inthisstudy,threemeasuresrelatedtolinearhabi- tatswereincorporated: theaggregationofallfieldborders,and theaggregationoflinearhabitatshavingasemi-naturalcompo- nents,bothpermanent and theirsubset, shrubbyfieldmargins.

Birdspeciesrichness,densitiesandcommunitycompositionwere significantlyrelated toeachof thesemeasures.Theirindividual influencescouldnotbeclearlyseparated,sincethemeasureswere notmutuallyexclusive.However,theaggregationofshrubbyfield marginswasclearlythemostrelatedvariableofbirdabundance, whichdrewtheothermeasures.MultivariateanalysisofRDAalso revealedthattheaggregationsoftheshrubbyandpermanentmar- ginswerebetterpredictorsofthebirdcommunitythanthenumber ofmaturetrees,proxyforcoverofmid-fieldwoodlots.Thismay suggestthatincomplexagriculturallandscapesthelengthoraggre- gation ofwell-vegetated field marginsact asefficient variables indescribing bird communities, andthis findingmaybeuseful whenseekingoptimalbiodiversityindicators(deHeeretal.,2005;

Morelli,Jerzak,&Tryjanowski,2014).

In contrast, the length of “all” ﬁeld margins that may well describeland-usepatterns,appearedlessusefultodescribebird indices.Inopenplots,birddensitiesandspeciesrichnesswerevir- tuallynotrelatedtothemarginaggregations,suggestingthateven adensemosaicofﬁeldscannotguaranteearichbirdcommunity whenthemosaicisnotsupplementedwithshrubs,treesorother microhabitats(Tryjanowski,Sparks,Jerzak,Rosin,&Skórka,2014).

In thisstudy, merely4–9breedingspecies werenoted in open mosaics(i.e.,plotshavingrichland-usepatternsbutdevoidofhigh vegetation).Therefore,ﬁeldmarginswithasemi-naturalcompo- nentandothernon-croppedhabitatsseemtobemoreimportant forthebirdcommunitiesthanland-use(Berg,2002).

Theimportanceoffieldmarginswasalsostressedbyidentify- ingthehabitatassociationswithbirds.Insmallarea,non-cropped habitatswereoccupiedbymostbreedingpairs,includingmostof thedominantspecies(excepttheopenfarmlandspecies).Most recordedspecies(81%)wereassociatedwithfieldmargins.More- over,thehabitatcategoryofmid-fieldwoodlotswassimilartofield margins,andwasdistinguishedonaccountofnon-linearshape.

Numberofbreedingbirdpairsinthewoodlotsandfieldmargins couldthenbemerged,increasingtherelativesignificanceofthese semi-naturalhabitatscomparedtocropfields.

Altogether,thesefindingsare consistentwithearlierstudies that infarming systemsonly a mosaic ofvarious field margins andothermarginalhabitatfeaturesensurearichspectrumofbird communities(Wuczy ńskietal.,2011).Thedataalsoconfirmthat amongvariouslinearfeatures,themarginspartiallycoveredwith highvegetation,suchastreelinesandhedgerows,playacrucial roleforshapingfarmlandbirdcommunities(Sandersonetal.,2009;

Whittinghametal.,2009).

Smallsamplesize(=12)wasthemainlimitationofthisstudy, precludingsomeanalyzes.For example,apparentdifferencesin bird communitiesbetweenthesubsamplesof openmosaic and openplainplots were not conﬁrmedin statisticaltests, proba- blyduetosmallsample sizes. Thelimitationwascompensated withothermethodologicalassumptions:relativelylargelandscape plots,thelaboriousmappingmethod,countingthecompletebird communities. For organizational reasonsI also couldnot avoid thecountstobeconductedindifferentyearsintheshrubbyand openplots.However,greatdifferencesinhabitatstructurebetween thesegroupsofplotswereprobablymuchstrongerthantheyear effects,sincetheinclusionoftheyearvariableintostatisticalmod- elswasnotsatisfactory.Itwasadditionallyconﬁrmedbyverylittle between-yeardifferencesinshrubbymosaicplots.Finally,thedata forthisstudywerecollectedseveralyearsago,andatpresentsome deteriorationinbiodiversityvaluescouldbeexpectedduetodetri- mentalchangesintheagricultureafterEUaccession(Sanderson etal.,2013).However,itisunlikelythatthedifferencecouldaffect thegeneraldistributionofbirdcommunitiesandtheconclusions presented.

Thefutureofbiodiversity-richfarmlandsisstillofmajorcon- cern,especiallyinthecontextoftheimpendingcurrentreformof