Waders, Hedgehogs and Machair: Research and Conservation Lessons from the Outer Hebrides

Waders, hedgehogs and machair: research and conservation lessons from the Outer Hebrides

DIGGER JACKSON

ConservationScience Department, Royal Society for the Protectionof Birds, Dunedin House, Edinburgh, EH4 3TP UK, e-maih digger.jackson @ rspb. org. uk or digger_dbj@ hotmail. com

Jackson,D. 2003. Waders, hedgehogsand machair:research and conservationlessons from the Outer Hebrides. Wader Study Group Bull. 100: 14-19.

In 1974, the hedgehog,a medium-sizedinsectivore native to the UK mainlandand most of Europe,was de- liberatelyintroduced to one of the islandsin the OuterHebrides, Scotland. The impactof theseanimals on the island'sinternationally important breeding waders was studiedby monitoringwader populations, meas- uringnesting success, identifying causes of nestfailure and through a predatorremoval experiment. It was concludedthat egg-predationby hedgehogshad causedlarge populationdeclines in four waderspecies. Studiesof the hedgehogssuggested that they find nestsincidentally whilst foraging for invertebratesand that thereis unlikely to be a density-dependentrelationship between nest density and the risk of hedgehog predation.There are considerablepractical difficulties in tacklingthe hedgehogproblem and achieving successfullong-term wader conservation. Challenges include preventing hedgehogs from spreadingto parts of the islandsthey have not yet colonisedand, wherethey are present,reducing their densityto levelsthat allow waderproductivity to increasesufficiently to allow populationrecovery. The storyof wadersand hedgehogs in the OuterHebrides comains a numberof lessonsof wide applica- tion. In particular,it underlinesthe dangersof introducingto islandsspecies that may be nativeon the nearby mainlandand which, at first sight,appear to poseno seriousrisk to islandwildlife.

INTRODUCTION smallerislands and are linked by tidal strandsand man-made causeways.On theseislands, the combinationof soilsde- The negativeimpacts of introducedmammal predators to rived from wind-blownshell sand, a cool,wet, windy climate islandbird communitiespresents a major word-wide chal- and low-intensity crofting agriculturehas resultedin the lenge to bird conservation.Although the most celebrated developmentof the habitatknown as "machair".This con- losers in this processare island endemics and seabirds sistsof a mosaicof dry and damp semi-naturalgrasslands, (Atkinson 1996), seriousimpacts to breeding waders are marshesand standingwater and is ideal breedinghabitat for being increasinglydemonstrated (Jackson & Green2000, six wader species.These are dunlin Calidris alpina, ringed Dowding& Murphy2001). Giventhat some Southern Hemi- plover Charadrius hiaticula, commonredshank Tringa spherewader speciesare confinedto islands,and that large totanus, common snipe Gallinago gallinago, Eurasian numbersof widespreadNorthern Hemisphere species breed oystercatcherHaematopus ostralegus and northernlapwing on islands,the issue of predator introductionsto islands Vanellusvanellus. The first full wadersurvey of the Uistsin shouldbe consideredas one of the "big issues"facing wader 1983 estimatedthat these six speciestotalled at least17,000 conservationin the 21 st century. pairs (Fuller et al. 1986), includingabout 25% of the total This paper summarisesthe main resultsof researchinto UK populationsof ringedplover and dunlin. the impact of a recentlyintroduced mammal predator, the The Uist breedinggrounds are of very high conservation hedgehogErinaceus europaeus, on the internationallyim- value,in particularbecause wader densities are exceptionally portantwader populations breeding on the Uistsin the Outer high comparedto thosereported from otherareas (densities Hebrides of Scotland. The stories of the Uist waders and frequentlyexceed 100 pairs km-2). Apart from the otter Lutra hedgehogsand the ongoingattempts to addressthe birds' lutra (a speciesthat forages almost exclusively in waterand conservationneeds, provide somevaluable lessons. These posesno threatto waders),the Uists have no nativemammal shouldbe particularlyhelpful in assessingthe threatsto predators,and this is probablyone of the key factorsallow- wadersfrom introducedmammals and finding solutions else- ing high breedingwader densities to be achieved.Over the where. years,humans have introducedseveral mammal predators, namelyrat Rattusnorvegicus, cat Felix domesticus,polecat BACKGROUND: LIFE BEFORE HEDGEHOGS ferretMustelofuro, European hedgehog and American mink Mustelavison. Most of theseintroduced predators have been One of the largestconcentrations of breedingwaders in Eur- presenton the Uists for a long time, but two are recentar- opeoccurs on the 250 km 2 coastal plain lying along the west rivals.The hedgehogwas introduced to SouthUist in 1974 sideof the islandsknown as the Uists. The Uists comprise and mink were first noted on North Uist in 2000, having South Uist, Benbeculaand North Uist and certain adjacent colonisedfrom islandsto thenorth where they escapedfrom

Bulletin 100 April 2003 14 Jackson: Waders, hedgehogs and machair 15

Table 1. The estimatedchange in wader populationsbetween 1983 rapidspread was almost certainly aided by humans,particu- and 2000. larly the colonisationof southernNorth Uist (Jacksonet al. in press).Today, ten yearslater, the distributionof hedge- Species South Uist and North Uist and hogson the Uists is littlechanged. They are common through- Benbecula adjacent islands out SouthUist andBenbecula, particularly in machairhabi- Redshank -41% +51% tats, but, apart from a small and somewhatisolated area in Lapwing -31% +24% the south,they are absentfrom North Uist and its adjacent Snipe -57% - 2% islands(Jackson et al. in press). Dunlin -56% -30% Ringed plover -56% -49% WADER DECLINES Oystercatcher +21% +55% The first evidence that all was not well for the Uist's waders,came from the resultsof routinemonitoring undertaken by the Royal Societyfor the Protectionof Birds (RSPB) in fur farmsin the 1950s.A studyof the breedingbiology of 1995 (Whyte & O'Brien, 1995). This showedthat numbers dunlin,redshank and ringed plover made on SouthUist in the of somespecies on SouthUist and Benbeculahad declined mid-1980sshowed that these waders generally enjoyed high by 30-60% sincethe 1983 survey.This result came as a sur- breedingsuccess and that the populationswere flourishing prise.At this stage,the reasonfor the declinewas unknown (Jackson1988, 1994). This studytook placebefore hedge- andso research was started by theRSPB the following year. hogsbecame properly established and has since been invalu- A comprehensivewader survey in 2000 allowed a de- able in providingbaseline information against which later tailed assessmentto be madefor eachspecies of the spatial changescould be assessed.The studywas also important patternof populationchange since 1983 (Jacksonet al. in becauseit showedthat the waderswere thrivingalongside press).The moststriking aspect of thisanalysis is themarked rats, feral cats,and polecatferrets. north-southdivide in how wadernumbers have changed (Table 1). Overall,waders in the northernpart of the breed- THE SPREAD OF HEDGEHOGS ing grounds(North Uist and adjacentsmall islands)have faredmuch better than those in thesouthern part (South Uist For aboutten years after their deliberateintroduction to the and Benbecula).Numbers of dunlin,redshank, snipe and southend of SouthUist in 1974,hedgehogs were restricted lapwinghave eachundergone large to moderatedeclines in to withina few kilometresof the releasesite and they were the south, whereas in the north their numbers have either relatively few in number (Morton 1982, Jacksonet al. in increased(lapwing and redshank) or declinedby muchless press).This meansthat the 1983 wadersurvey took place (dunlinand snipe).Ringed plover show a differentpattern, beforehedgehogs could have had any significanteffect on having undergonelarge declineseverywhere although waderpopulations. After this,hedgehogs spread north rela- slightlymore so in the south.Oystercatchers also showa tivelyrapidly and by theearly 1990s they were present along differentpattern, with the speciesincreasing in all areas. the length of South Uist and Benbeculaand had even col- However,the size of theincrease has been nearly three times onisedthe southernpart of North Uist (Angus 1993). This greaterin the north.

lOO

8o n25 n 96

2o n 59

S U Ist mld.1980s S Ulst mld-1990s N Ulst 1997 no hedgehogs many hedgehogs no hedgehogs

Fig.1. Dunlinhatching rates in the Uists in relation to the presence of hedgehogs. Nest survival rates were calculated using the Mayfield Method.

Bulletin 100 April 2003 16 Wader Study Group Bulletin

Plate 1. Hedgehogeating lapwingeggs. Introducedin 1974, the hedgehogis now common across large pads of the Outer Hebrides and a major predator of wader eggs.

Plate 2. Colour-ringedschinzii race dunlinbreeding in machair habitatin the Outer Hebrides Dunlin are one of the species that that has undergone large declines because of egg predation by hedgehogs.

Bulletin 100 April 2003 Jackson: Waders, hedgehogs and machair 17

The north-south difference in the way wader numbers linking the signsleft behindwith the exacttime of nestfail- have changedreflects the distributionof hedgehogs,i.e. ure was obtainedusing data-loggersset up to record nest hedgehogsare presentthroughout the southernareas and temperatureevery few minutes.The loggersshowed that all absentin the northernareas (Jackson et al. in press).How- but one of the nine lossesascribed to gulls occurredduring ever,by itself,this is purelycircumstantial evidence that the daylight and all 17 of the lossesascribed to hedgehogs two may be connected. occurredat night (Jackson& Green2000). It was possible, therefore, to identify the cause of almost all nest failure DECLINE IN NEST SUCCESS events with confidence. On the basisof the signsleft at failed nests,it was esti- A pilot studyby ScottishNatural Heritage(SNH) in 1995 matedthat on SouthUist in the mid-1990s, hedgehogswere into the possibleimpacts of hedgehogsfound that some responsiblefor at least60 % of the nestfailures of dunlin, hedgehogscats contained fragments of wadereggshell (Watt redshankand snipeand 35% of lapwingnest failures. How- 1995). Of course, showingthat hedgehogssometimes eat ever, hedgehogsappeared to be the causeof only about 10% wadereggs did not meanhedgehogs were the causeof the of ringedplover and oystercatchernest failures (Jackson & waderdeclines. Far more evidencewas required to quantify Green 2000, RSPB unpublisheddata). what impact,if any, hedgehogswere having. Largenumbers of wadernests were monitored in 1996/97 HEDGEHOG REMOVAL EXPERIMENT at siteson SouthUist (wherehedgehogs were common)and North Uist (wherehedgehogs were absent)and nestsurvival A predatorremoval experiment was conducted on SouthUist rates calculated.For three species(dunlin, redshank,and in 1998 (Jackson2001). The mainpurpose of thiswas to test ringedplover) it was possibleto comparethese values to the resultsof the nest-monitoringstudies and to show that correspondingmeasures made on the sameSouth Uist sites conservationmeasures could be worthwhile.The experiment in the mid-1980s,before hedgehogs established. consistedof making two large exclosuresusing hedgehog- The 1990s nest survival ratesfor three speciesthat had prooffencing before the start of thewader nesting season and undergonelarge declineson SouthUist (dunlin, redshank removingall hedgehogsfrom within. Dunlin and lapwing and snipe)were very low (10-20%) in SouthUist and rela- nesthatching rates inside the exclosureswere then compared tively highin North Uist. Furthermore,for the threespecies with thosein adjacentcontrol areas and alsowith ratesfor wherea comparisoncould be made,the mid-1990sSouth the previousyear at the samesites. The experimentshowed Uist nestsurvival rates were much lower than they had been that hatchingrates were approximately2.4 times higher in in the mid-1980s (Jackson& Green 2000). These differences the absenceof hedgehogs(Jackson 2001). are well illustrated by the nest survival rates for dunlin (Fig. 1). HEDGEHOG FEEDING ECOLOGY Mid-1990s nest survivalrates for oystercatcher,the only speciesthat has not declined in SouthUist werehigh on both The natureof thepredator-prey relationship between hedge- SouthUist andNorth Uist. Lapwingnest survival in the mid- hogsand wadershas important implications for predicting 1990s was moderateon SouthUist, where this specieshad how wadersmay fare in the future and for designingeffec- undergonemoderate population decline, and high on North tive conservationmeasures. The observedhigh rate of egg Uist, where numbershad increased.Finally, mid-1990s nest lossto hedgehogs,superficially suggests that hedgehogsare survivalrates for ringedplover, the speciesthat had declined capablenest-finders and that eggsare an importantpart of throughoutthe islands, were low in both North Uist and theirdiet. However,research into the feedingecology of Uist SouthUist. They also showthat for all six speciesthere is a hedgehogsindicates otherwise. Based on the estimated strongpositive correlation between recent population change numberof eggslost and the densityof hedgehogspresent, and nest survival (Jackson& Green 2000). Jacksonand Green (2000) calculatedthat wader eggs con- tributedonly 2-5% of the energyintake of hedgehogsdur- CAUSE OF DECLINE IN NEST SUCCESS ing the wadernesting-season. Similarly, eggshell fragments were foundin about2% of hedgehogdroppings at this time Accurate identification of the cause of nest failure was essen- of year.Thus, wader eggs are of little importanceto hedge- tial to determine the relative importance of different nest hogsand there is no expectationthat hedgehogs will be short predatorsand other causes of failure.On the SouthUist study of food without eggs. sites,observations during daylight and spot-lampsurveys at Thereare two methodsthat hedgehogscould use to locate night showedthat there were few candidatepredators pre- nests:on the one hand they could actively look for nests; sent,and that two specieswere much more frequentlyseen alternativelythey couldcome across them passively during thanothers, namely common gulls Larus canus (during day- their normalforaging for invertebrates.To discoverwhich time) and hedgehogs(at night). Nest predationevents by methodthey use, Uist hedgehogs(n=l 8) were fitted with gulls and hedgehogswere witnessedon severaloccasions radiotags and beta-lights (a smalldimly glowing phospho- andsigns remaining at the nestsites were examined(Jackson rouslight) so that they couldbe followedall night without & Green2000). It was foundthat the signsleft by thesetwo disturbingthem. This studyfound no evidenceof hedgehogs predatorsare very differentand distinctive. Gulls leavebe- searchingfor eggs,but on severaloccasions hedgehogs that hind an empty undisturbednest, whereas nests taken by were foragingnormally for invertebrateswere observeden- hedgehogshave a very disturbedlining andthere are always counteringa nestand then eatingthe eggs(RSPB unpub- remainsof eggshellsin the vicinity.Furthermore, these shell lisheddata). A smallsample of hedgehogstracked, using the fragmentsare always licked clean,typically have chewed "line-and-spool"technique, was observedto passby nests edgesor teethholes and sometimestwo or threehalf-egg- only a few metresfrom their routes (RSPB unpublished shells are stacked inside one another. Additional evidence data). Therefore,it appearsthat hedgehogsneed to be very

Bulletin 100 April 2003 1 8 Wader Study Group Bullebn close to a nest before they can detectit. Exactly how close ment conservationagency) and RSPB was formed in 2000 is not known (andit is probablyinfluenced by wind andhu- to developand deliver conservationmeasures. Large areas midity), but it is probablyless than one metre. Thus it seems of the Uists are designatedas Special ProtectionAreas for that hedgehogsare not expert nest finders.So why are so breedingwaders under the EuropeanUnion's Birds Direc- many nestslost to hedgehogs? tive, andthe UK Governmentis obligedto maintainpopu- Three factors combine to explain why so many wader lations within these areas in a "favourable conservation nestsare foundby hedgehogs.These are the relativelylarge status". distancetravelled each night by hedgehogs,high hedgehog Preventingfurther hedgehogspread in North Uist is the densitiesand the relatively long periodthat eggsare at risk top priority and this is being attemptedby erectingbarrier (the laying and incubation periods combined for these fencesand trappingand removinghedgehogs. Ultimately, waders is about 27 days). The all-night tracking of Uist the objective is to achieve wader population recovery hedgehogsshowed that, on average,males travel aboutfour throughoutthe Uists.The feasibilityof reducinghedgehog kilometres each night during their foraging and females densities,and of total removal,will be investigatedthrough abouttwo kilometres(RSPB unpublisheddata). If, on aver- practical trials and continued detailed researchinto Uist age, a hedgehogcan only detect nestswithin 0.5 m of its hedgehogdemography, habitat use and dispersal. foragingroute then males would effectively"search" an area Conservationwork is still at an early stageand it will be 4 km x 1 m, and females half this. Survey work has shown some years before the likelihood of successof different thatthe instantaneoushedgehog density on the Uist machair options can be fully evaluated. It is already clear that the is typicallyaround 30 animalskm -2 and that the sex ratio is sheersize of theislands (750 km2), the difficulty of detect- approximately1:1 (Jackson& Green 2000, RSPB unpub- ing and catchinghedgehogs when at low densityand their lished data). Based on these figures, the accumulateddis- high fecundityand dispersalrates make it unlikely that to- tancetravelled by foraginghedgehogs each night in a hypo- tal removalcan be achievedwith currenttechnology. How- thetical 1-km squareof the wadernesting grounds would be ever, reducinghedgehog densities to levelscompatible with 90 km. If each animal' s route is random relative to the routes waders(say an 80% reduction)should be relativelystraight- of others(which appearsto be the case)then 8.6 % of the forward.The drawbackof this approachis that it requiresa groundwould be effectively "searched"each night. perpetualeffort andwill thereforebecome very expensive in This calculationof the theoreticaldaily risk of nestdetec- the long run. Furthermore,any conservationgains would tion is similar to the ca. 5-7% daily lossrates to hedgehogs soonbe lost if (as is likely) this effort ceasedin the future. observed on South Uist for nests of dunlin, redshank, and Perpetualcontrol could help "buy time" whilst new tech- snipe(Jackson & Green2000). The abovecalculation, how- niquesthat maketotal removalfeasible are developed,such ever,is simplisticbecause it doesnot takeinto accounthabi- as immuno-sterilization. tat selectionby hedgehogsand birds andrelies on a number In the UK, hedgehogshave a high positivepublic profile. of uncertainassumptions, for examplethe effective search As a result,the issueof hedgehogsand wadershas attracted with of hedgehogroutes. Nevertheless, it is probablethat it considerablemedia attentionand there is significantpublic correctlydescribes the basisof the risk and its approximate concernfor the welfare and fate of Uist hedgehogs.These magnitude.Habitat selection very likely explainswhy ringed concerns,together with the partial legal protectionafforded ploverssuffer fewer lossesto hedgehogsthan the othersmall to hedgehogs,significantly constrain the rangeof techniques wader species.In the Uists, ringed ploversnest mainly on available for controlling them and have causeddelays in bare sandyhabitats such as ploughed ground and recent fal- startingconservation work. (At the time of writing, six years low (last season'scereal stubble), habitatsthat hedgehogs after it was shownthat hedgehogsare a major problem,no generallyavoid when foraging (RSPB unpublisheddata). hedgehogcontrol has yet taken place althoughwork will If, asis almostcertainly the case,hedgehogs come across commence on North Uist in 2003.) This contraststo the situ- wadereggs by accidentand eggs are of trivial importanceto ationfor Americanmink, a speciesthat hasbeen demonised them, thendensity-dependent negative feedback is not to be by the media. Large-scalelethal controlof mink startedon expectedin this predator-preyrelationship. Unlike the risk the Uists within a few months of their first detection. posed by a predator that hunts for prey and switches to alternativeprey when low densitymakes hunting unprofit- CONCLUSIONS able (as, for example, in the caseof gulls feeding on wader eggs)the theoreticalrisk posedto wadereggs by hedgehogs The spatial and temporal coincidencebetween hedgehog will not diminish as wader nestdensity declines. The risk is colonisationand wader declines,together with the data on purely a function of hedgehogdensity and how far they the extent and causes of nest failure and the results of the travel. This has important implications for conservation. hedgehogremoval experiment show that the introductionof First, it is theoreticallylikely that hedgehogswill causecon- hedgehogshas had a large negative impact on four wader tinuing wader declines and could possibly causethe local species.However, hedgehogsdo not appearto be a major extinctionof somespecies (Jackson & Green2000). Second, direct factor in the declineof the ringedplover. The reasons to be effective, conservationmeasures will needto greatly for the declinein this speciesare not fully understoodbut are reducehedgehog density on the waderbreeding grounds. probably linked to land managementand changesin the severity of egg-predation by gulls (see Jacksonet al. in TOWARDS A SOLUTION press). The nature of the predator-prey relationshipbetween It is beyond the scopeof this paper to describein full the hedgehogsand waders suggests that the risk of egg-predation processand ongoingwork aimed at wader conservationon by hedgehogsis unlikely to be modulatedby directdensity- the Uists.The Uist Wader Project,a partnershipbetween The dependenceand that the risk is simply a functionof hedge- ScottishExecutive, ScottishNatural Heritage (the govern- hogdensity. If thisis so,there is a high likelihoodthat, with-

Bulletin 100 April 2003 Jackson: Waders, hedgehogs and machair 1 9 out conservationmeasures, some wader species will decline ACKNOWLEDGEMENTS furtherand may evenbecome locally extinct. Contrary to this rather pessimisticforecast, there is some evidencethat in ForemostI wouldlike to acknowledgethe major role thatthe recentyears the ratesof declineon SouthUist andBenbecula late Peter Evans played in Uist wader research.Peter was have slowed and some speciesmay have even stabilised involvedfrom the startand was instrumentalin makingit (Jacksonet al. in press).This may be becauseegg predation possiblefor me to studythe breedingwaders on SouthUist, risk is locallymodulated by habitatcomposition and scale (in first for an undergraduateproject in 1983 and later for my ways that are not yet fully understood)or becausedensity- doctoralstudy, which Peter supervised. I thankhim not only dependenteffects are acting on otheregg predators or at other for the tuition,encouragement and wisdomthat he gaveme stagesof the waders'life cycle. as a student,but alsofor his friendshipand giving me, and Apart from oystercatcher,Uist breedingwaders do not manyothers who passedthrough Durham University, a spe- presentlyhave a favourableconservation status. Large-scale, cial appreciationof waders.Although not involveddirectly long-termconservation work will be requiredto restoreand with the more recent research,Peter keenly followed the safeguardthese populations. Although tackling the hedgehog developingstory and gave wise counsel. problemis a top priority,this alonewill not be sufficient.Of I would also like to thank the many people who have equal importanceis making sure that the unique machair helpedwith wader and hedgehogsstudies in the Uists, and habitatmosaic of the Uists is maintainedand appropriately to the islandersand landowners for giving free accessto the managedby traditionalcrofting. wader breedinggrounds. Most of the recent researchwork The storyof the Uist waderscontains a numberof useful hasbeen financedby RSPB, thanksto its million members. lessons: David Gibbons and Iain Mackenzie are thanked for their commentson a draft manuscript.I would alsolike to thank 1. The value of baseline information. Without the 1983 sur- HumphreySitters for his enthusiastichelp and encourage- veys and mid-1980s data on wader breedingsuccess, it ment with this paperfrom inceptionto completion. would havebeen much harder to demonstratethe impact of hedgehogson waders and make the case for conser- REFERENCES vationaction. It is likely thatmany of theeffects of predator introductionsgo unnoticedbecause there are no base- Angus, S., 1993. Hedgehogsin the Western Isles in 1991. Hebridean line data. Naturalist 11: 73-76. Atkinson, I.A.E., 1996. Introductionsof wildlife as a causeof species 2. The value of routinemonitoring. At the time of the 1995 extinctions. Wildlife Biology 2: 135-141. surveys,no one suspectedthere was a problem, despite Dowding, J.E. and Murphy, E.C., 2001. The impactof predationby considerablebird watching activity on the islands and introduced mammals on endemic shorebirds in New Zealand: a con- someareas being naturereserves. servationperspective. Biol. Cons.99: 47-64. 3. The benefitsof multiple evidence.The casethat intro- Fuller, R. J., Reed, T. M., Buxton, N. E., Webb, A., Williams, T. D. and ducedhedgehogs have causedlarge deleteriousimpacts Pienkowski,M. W., 1986. Populationsof breedingwaders Charadrii andtheir habitats on thecrofting lands of theOuter Hebrides, Scotland. to Uist wadersis compellingbecause it is basedon sev- Biol. Cons. 37: 333-361. eral linesof evidence:the timing of hedgehogspread, the Jackson,D.B., 1988. Habitat selectionand breedingbiology of three spatialand temporalchanges in waderpopulations, the speciesof waderin the WesternIsles of Scotland.Unpublished Ph.D. declinesin waderhatching rates, the proportionof nests thesis,University of Durham. lost to hedgehogs,a predatorremoval experimentand Jackson,D. B., 1994. Breedingdispersal and site-fidelityin threemono- studiesof the predator'sfeeding ecology. Initially many gamouswader speciesin the WesternIsles, UK. Ibis 146: 463-473. peoplewere scepticalthat hedgehogs, a specieswith the Jackson, D.B., 2001. Experimentalremoval of introducedhedgehogs improveswader nest successin the WesternIsles, Scotland.J. App. reputationof a "harmlessinsectivore", could causesuch Ecol. 38: 802-812. a largeimpact. The removalexperiment has been particu- Jackson,D.B. and Green, R. E., 2000. The importanceof the introduced larly valuable,as it testedthe conclusionsof the nestsur- hedgehog(Erinaceus europaeus) as a predatorof the eggsof waders vival study and practically demonstratedthe value of (Charadrii)on the machairin SouthUist, Scotland.Biol. Cons.93: 33- hedgehogremoval. The multipleevidence was alsoim- 348. portantin demonstratingthat hedgehogs are not the direct Jackson, D.B., Fuller, R.J. and Campbell, S.T., in press. Long-term causeof declinesin ringedplover. populationchanges among breeding shorebirds in the Outer Hebrides, Scotland,in relationto an introducedmammalian predator. Biol. Cons. 4. The importanceof understandingthe nature of the rela- Morton, E., 1982. Hedgehogsin SouthUist. HebrideanNaturalist 6: 46- tionshipbetween predator and prey. The expectedlack of 47. directdensity-dependent effects between nest density and Watt, J., 1995.Hedgehogs and ferrets on the SouthUist machairs;a pilot predationrisk has importantimplications. studyof predationon groundnesting birds. Unpublished report, Scot- 5. The importanceof knowing the "enemy". A thorough tish Natural Heritage,Inverness, UK. understandingof Uist hedgehogbiology is a key element Whyte, C. and O'Brien, M., 1995. Changesin the numberof waders breedingon machair habitatson the Uistsand Benbecula,1983-1995. underpinningthe currentdevelopment of conservation Unpublishedreport, Royal Societyfor the Protectionof Birds, Edin- solutions. burgh. 6. The importanceof publicopinion. Public concern for the welfareof well-liked "problem"species, like the hedgehog, can constrainand delay controlmeasures. 7. The dangersof introducingto islands,mammals from the nearby mainland.Hedgehogs are native on the UK mainlandand there is no legislationprohibiting their in- troductionto partsof the UK wherethey are not native, such as islands.

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