Breeding waders around the Duddon estuary in 1994

D. Jo Radford

Radford, D.J. 1995. Breedingwaders around the Duddon Estuary in 1994, Wader Study Group Bull. 77: 27-31. The Duddon Estuary is a site of internationalimportance for wintering and migrating waterfowl. In 1994 the first comprehensivesurvey of the waders breedingaround the estuary was undertaken. Oystercatcher Haematopus ostralegusand Ringed Plover Charadrius hiaticula nested at high densitieson slagbanks, but the estuary populationof Ringed Plover had declinedsince national surveys in 1973/74 and 1984. Lapwing Vanellusvane#us and Curlew Nurneniusarquata densitiesin fields were similar to densitiesat the best sites in lowland Scoffand. Redshank Tringatotanus density on saltmarshwas very low relativeto 'good'sites such as are found in Morecambe Bay and Essex, but their density in fields was high in comparisonwith other sites in northernEngland and Scotland. Small numbers of Dunlin Calidrisalpina, Snipe Gallinagogallinago and Common Sandpiper Actirishypoleucos were found. A proposal for a power generating barrage, overgrazing on some saltmarsh and fields. undergrazingat and human disturbanceare the main threats to breeding waders.

D.J• Radford, c/o RSPB Minsmere Reserve, Westleton, Saxmundham, Suffolk IP17 3BY, U.K•

INTRODUCTION

Duddon Bridge

TheBirds of Estuaries Enquiry (now the Wetland Bird Habitats Broughton-in- Survey - WEBS) supplementedby the fieldworkof a few Saltaarsh dedicated individuals has demonstrated that the Duddon Slagbank Estuary is a site of internationalimportance for wintering Beach Lady Hall and migratingwaterfowl (e.g. Waters & Cranswick 1993), Foxfield but breeding waterfowl have never been comprehensively Fields surveyed. Terns (Sterna spp.) have been monitored •ne syst•s annuallysince 1986 (Hutcheson1987, 1988; Callion 1989 - 1994; McAIone 1995), Ringed Plovers Charadrius h•aticulawere surveyedas part of national surveys in Scale 1973/74 and 1984 (Prater 1976, 1989), waders at North Kirkby- were covered in a survey of saltmarshes in 1985 (Allport et al. 1986), and Shelducks Tadorna tadorna were surveyednationally in 1992 (Wildfowl & Wetlands

Trust unpubl.).

The recent proposalfor an energy generatingbarrage and Haverig• road across the mouth of the estuary (ETSU 1994), and ,k.•V•Hodbarrow NR the development of an.estuary management plan (Bayliss 1994) have highlighted'the need for an assessmentof the Askaa-in-Furness estuary'simportance for breedingwaders, especiallyin DUDDON ESTUARY the context of national declines in the breeding / , populationsof many species of waders (Batten et al. 1990). Sandscale }laws N R

STUDY AREA

The Duddon Estuary lies to the west of the Furness Peninsulain south-westCumbria (Figure 1). Its length North Walney N R from Duddon Bridgeto North Walney is 15 km, but much of the estuaryis only 2-3 km wide until it opens into the Barrow-in-Furness Irish Sea between Haverigg and Walney Island. With the exceptionof small areas of mixed mud, sand and pebbles Figure!o Locationof studyareas aroundthe DuddonEstuary. at Haverigg and in the north end of Walney Channel, the estuaryto the south of Millom and Askam-in-Furness•s

27 dominated by extensiveand highly mobile sand flats, and this was consideredto be preferableto walking on the large sand dune systemswhich lie on both sides of the saltmarsh, where the short turf allowed most waders to be mouth at Haverigg,Sandscale and NorthWalney. seen easily. For the areas outsidethe nature reserves, the numbers of pairs of the six most numerousspecies The estuary becomes progressivelymuddier from Millom were assessed usingthe followingmethods and Askam-in-Furness,and the middle and upper reaches recommended by Bibby et ai. (1992) and O'Brien & Smith are flanked by saltmarsh which has developed since the (1992): most recent land claims in the 19th century. Most of the saltmarshand the surroundingagricultural land is grazed Oystercatcher number of paired individuals by sheep and cattle, and there are areas of lowland raised Haematopus (maximum across three mire between Kirkby-in-Furnessand Foxfield, and near ostralegus visits) divided by two - pairs Lady Hall. Ringed Plover nest or territorial bird Charadrius hiaticuL,? (average of three visits) = During the late 19th and early 20th centuries,mining and pair processingof iron ore had dramatic effects on the landscapearound Millom and Askam-in-Furness,creating Lapwing maximum number of HodbarrowLagoon and the slagbanks at BorwickRails, Vane#us vaneflus individuals(average of first Millom (21 ha), Hodbarrow(8 ha) and Askam-in-Furness two visits) divided by two = (4 ha). Slag is a waste productfrom the iron smelting pairs processon whichvegetation develops very slowly. The Duntip slagbanks are used by birds which normally nest on Duddon criteria - bird(s) on shingle, and today are regionallyimportant nestingareas Calidnsalpina site during season for waders and terns. Snipe maximum number of Gallinagogallinago drummingbirds

Curlew SURVEY METHODS number of paired individuals Numeniusarquata (maximumacross three visits) divided by two = pairs In recent years breedingwaders at the nature reserves on either side of the estuarymouth at Hodbarrow,Sandscale Redshank number of birds (average of and North Walney have been monitoredannually by the Tringa totanus first two visits) = number of reserve wardens. In 1994 this information was combined pairs with the resultsof surveywork undertakenby local Common Sandpiper Duddon criteria- bird(s) on BoEE/WeBS counters,either in the government'sTraining Actitishypoleucos site during season for Work programmeor voluntarily. The surveyarea was divided into sections based on habitat: saltmarsh, slagbanks,dunes and dune slacks, beach, and fields Observations on the nature reserveswere more frequent where they were adjacentto dune systemsor saltmarsh. than elsewhere, allowing a more accurate assessment of numbers to be made. Although no evaluation of the differences between resultswas undertaken, any under- Visits were made to each section duringthe morningon at estimates outsidethe nature reserveswere probably least three occasions between mid April and mid June insignificant. (first visit: 15-30 April; secondvisit: 1-21 May; third v•sit: 22 May-18 June), and also at least once at dusk to record Snipe Gallinagogallinago. Observationsof birdson the saltmarsh and adjacent fields were made from the embankmentbetween the two habitatsusing a telescope;

Table 1. Breedingwaclers around the DuddonEstuary in 1994, Totalnumber of pairs,and densitiesin the fourmain habitats,

Species Estuarytotal Saltmarsh Fields Slagbanks Beach

no. density no. density no. density no. density Oystercatcher 130 60 12.8 0 43 130.2 27 2.0 Ringed Plover 51 0 0 24 72.7 27 2.0 Lapwing 85 29 6.2 38 13.1 7 21.2 0 Dunlin 1 0 0 1 0 Snipe 6 0 4 1.4 0 0 Cudew 12 3 0.6 9 3.1 0 0 Redshank 59 22 4.7 29 10.0 1 0

Habitat 'area'* 4.70 2.89 0.33 13.5 km2 km2 km2 km * unitsof measurement forhabitats and densities: saltmarsh, fields and slagbank inkm 2 (densitiesinpairs/km2), beach in km (densities in pairs/km)o

28 Table2. Averagewader densities (in pairs/km 2) in fields around the population is considerablyhigher than DuddonEstuary in 1994 comparedwith surveys of lowlandbreeding indicatedin the New Atlas (Murray et al. 1995). wadersin Scotland(O'Brien 1994) and northernEngland (Murray et aL 1995). Ringed Plover Survey Lapwing Snipe Curlew Redshank Numbers were derived from apparentlyterritorial birds Duddon 1994 13.1 t .4 3.1 10.0 (usuallypairs)in all suitablelocations except Hodbarrow, Scotland 1992 11.3 5.2 3.4 3.9 where incubatingbirds are easy to observe(nine pairs on (keysites) 3 ha of suitable habitat). Numbers were probablyunder- Scotland 1992 2.2 0.5 1.4 0.1 estimatedat BorwickRails, Millom (13 pairs estimatedor• (randomsites) 21 ha). The three slag banks at Hodbarrow,Borwick N. England1993 3.0 0.1 1.7 0.2 Rails and Askam-in-Furr•ess(combined area 33 ha) helcl (randomsites) 1993 3.0 0.2 2.8 0•1 about three-quartersof the estuary population. Numbers (randomsites) breedingin Englandand Wales increasedby 20% 1993 6.8 0.0 3.7 0.1i betweenthe nationalsurveys in 1973/74 and 1984 (Prater (randomsites) II989), but the Cumbrian totals were 247 and '•90 pairs respectively(i.e. an apparent declineagainst the national Key sites (Scotland)are those consideredto be importantfor trend). breedingwaders by regionalconservation workers• Randomsites are a randomsample of lowlandsites of unknown In 1973/74 Hodbarrowand North Walney contributed65 status as breedingwader sites. pairs to the countytotal, and this figure was used in the 1984 estimate as these two sites were not counted that year (Prater 1989), but in 1994 the combinedtotal for RESULTS AND DISCUSSION Hodbarrowand North Walney was only 25 pairs. Reductions in areas of suitable nesting habitat in the last The results are summarised in Table 1. Densities of the 20 years at North Walney (developmentof vegetationon five most numerous specieswere calculatedfor the four 4 ha of shinglefollowing the cessationof grazing in 1971; main habitats used by breedingwaders, (saltmarsh, T. Jones, pers. comm.) and at Hodbarrow(vegetation fields, slagbank, beach) but not for the dune systems developmenton 5 ha of slagbank)cannot alone account where small numbers of waders nest in a complex for such a large decline; an increase in the use of beaches arrangementof microhabitats. Densitiesof Lapwing for recreationis likelyto be anotherfactor. Vaneflusvane#us, Snipe, Curlew Numeniusarquata and Redshank Tnnga totanus •n fields are comparedwith the Lapwing resultsof surveys of lowland habitats in Scotland in 1992•93 (O'Brien 1994) and northernEngland (Murray et Lapwingswere the most widely distributedof the species al. 1995) in Table 2. These data are not strictly coveredby this survey, usingfields, saltmarsh,slagbanks comparable,as the area coveredin the Duddon survey and dune slacks. There was considerable variation in the was much smaller than the total areas covered in the qualityof fields, which rangedfrom uniformshort turf to others. The original data are stored at the RSPB's poorlydrained ground dominated by rushesJuncus spp. Campfield Marsh Nature Reserve. Highest densitiesof Lapwingswere found on what was formerlyraised mire betweenFoxfield and Kirkby-in- The results from each species are considered below, with Furness. In contrastthere were few on heavily grazed referenceto the most recentlyavailable national fields, where there was little cover for eggs or chicks. populationestimates and trends. Averagedensity in fields(13.1 pairs/km2) is comparable to the average densityat 'key sites' in lowlandScotland in Oystercatcher 1992(11.3 pairs/km 2, O'Brien1994). The density on saltmarsh(62 pairs/km2) wasrelatively low; Allport et al. Incubatingbirds were often easy to see, especiallyon the (1986)recorded densities of upto 40 pairs/km2. slagbanks and grazed saltmarsh. Otherwise, birds (usuallypairs) apparentlyoccupying territories were taken In Englandand Wales, over 90% of Lapwingsbreed on as evidenceof breeding. Oystercatchersnested on agriculturalland, preferringto nest in fields cultivatedin slagbanks, saltmarsh and beaches, but had a clear the spring near to grass. Such sites combine bare preferencefor the slagbanks. The overall density ground,the most productivenest sites, with grass which concealsa patchy distributionwith some groups being is the best habitat for rearingchicks (Gibbons et al. 1994). almost colonial in places; for example, about 15 pairs nest The Duddon population•s a very small proportionof the on the 2 ha island at Hodbarroweach year. national population,but the decline in mixed farming in lowlandBritain combined with sharp increasesin stocking The Britishpopulation is increasingmainly as a resultof rates on grassland are leadingto reduced breeding range expansion inland into arable farmland in eastern numbersand productivity,and saltmarshesare likelyto (Gibbons et al. 1994). The combinedpopulation assume relativelygreater importancein the future. of Britain and Ireland represents about 20% of the European Oystercatchersbreeding outside the former USSR, although recent informationsuggests that the

29 Dun/in and tidal inundationcausing vegetation change from upperto lower saltmarshcommunities (Cook et al. 1994). Birds in breedingplumage were presenton the grassy In contrastto the low average densityon the Duddon islandat Hodbarrowduring the springand summer in saltmarshes,the high average densityin the fields(10.0 1993 and 1994, and singingwas heard. A female doinga pairs/km2) is probablydue to a largeproportion being broken-wingdisplay on 12 July 1994 was taken as proof poorly drainedand lightlygrazed. The loss of wet of breeding. Duniin breed on saltmarsharound grasslandsto drainageand agriculturalintensification is MorecambeBay in small numbers(Allport et aL 1986; J. probablythe cause of declineson inland sites (Gibbons et Wilson, pers. comm.), and may have bred on the aL 1994). saltmarsh to the north of Millom in the 1980s (D. Thexton, pers. comm.). Common Sandpiper

Snipe The preferredhabitat of this species, shingle banks and stony shores mainly by freshwater,,is found in the survey Birds were all recorded in areas of poorly drained pasture, area only at the head of the estuarynear DuddonBridge either at nests (three at Sandscale) or duringdisplay Its extentvaries with water conditionsand may be flights(drumming). There is little suitablebreeding insufficientfor breedingin some years. habitat in the survey area, but Snipe probablynest outside this area in the marshyfields and raised mires at the head of the estuary. CONSERVATION

Curlew The immediatethreat of a barrage acrossthe mouth of the estuary(ETSU 1994) has recededas a resultof a All recordsrelate to displayingbirds on the saltmarsh and change in governmentpolicy, but the proposalwill adjacent fields around the inner estuaryto the north of probablyre-emerge in the future as energyand transport Miiiomand Askam. The density in fields(3.1 pairs/km2) requirementsare reconsidered. Such a developmentis is similar to the average densityat 'key sites' in lowland likelyto have profoundeffects on the wildlifeof the Scotlandin 1992/93(3.4 pairs/km2, O'Brien1994). The estuary. improvementsto the road crossingnear Duddon dozen or so pairs recorded are but a fraction of the Bridgewere being consideredduring 1994, but the effect Cumbdan breedingpopulation, which is found mainly on on breedingwaders is likelyto be small. moorland,low intensitygrassland and raised mires, and which forms a significantproportion of the British Agriculturalpractices have an important influenceon population. many breedingwaders. Drainage of grasslandhabitats lowersthe water table and reduces food supply, and Redshank heavy grazingon pastureand saltmarshleaves nest sites more exposedand increasesthe chance of trampling. The Redshank is one of the hardest species to census, Aroundthe Duddon Estuary much of the saltmarshis especiallyat high densities. The saltmarshdensity of 4.7 heavily grazed by sheep. However, the complete pairs/km2 is verylow, probably a reflectionof the heavy cessationof grazing on the saltmarsh at North Walney grazing pressureto which most of the saltmarsh is also appearsto have had an adverse effecton breeding subjected(but see comment about North Walney below). waders. Between 1985 and 1994 numbers of pairs of At North Walney NNR four pairs were recordedin 1994, Oystercatcherdeclined from 16 pairs to zero, Lapwing but only two were on the saltmarsh (both on the upper declinedfrom 11 pairs to zero, and Redshankfrom 20-21 edge)where there were 20-21 pairs (density 53 pairs/km2) pairs to two. The site was describedby Allportet al. in 1985 (Allportet aL 1986). The saltmarshat North (1986) as "oneof the top ten in the countryfor densityof Wainey was grazed for centuriesuntil cattle grazing breedingOystercatcher" and "one of the best of the ceased in 1970, but by 1993 the cover of Sea-lavender surveyedsaltmarsh sites for diversityof breedingbirds", D7noniumvulgare and Sea Pursiane Ha/imione but clearlythis is no longerthe case. portu/acoideshad becomevery dense (T. Jones, pers. comm.), and is now probablytoo densefor breeding Reductionin grazing pressurewould improvemuch of the waders. Another importantinfluence on the saltmarsh at saltmarsh around the Duddon for most of the breeding North Walney is tidal inundation;80% of the area is wader species, but the reintroductionof light cattle grazing coveredby 20% of the high tides in the spring(T. Jones, seems necessaryat North Walney to restorethe pers. comm.). saltmarshas breedinghabitat. In contrastto the situation prevailingon the saltmarshes,the fields appearto support On the saltmarsh managed by the RSPB in Morecambe healthy numbersof most species; hopefullythey will not Bay (light cattle grazing), Redshanksnest at a densityof be degradedby increased drainage. Mechanismsexist to 47 pairs/km2, comparedwith 2-8 pairs/km2 on the heavily promote appropriatemanagement practicesfor the grazed saltmarshoutside RSPB control(J. Wilson, pers. improvementof wildlife habitats in the Lake District comm.). In 1993 the best Essex saltmarshfor Redshank EnvironmentallySensitive Area (ESA), but unfortunately held80 pairs/km2, butdeclines at somesites in Essex the low-lyingland aroundthe Duddon Estuarylies just since 1985 may be related to a combinationof erosion outsidethe ESA. However, it may be possiblefor managementagreements to be arranged for areas within

30 the DuddonEstuary Site of Special ScientificInterest; the 1990. Red Data Birdsin B#tain. Poyser,London. publicationof an estuary managementplan (Bayliss 1994) Bayliss,R. 1994. The DuddonEstuary: a partnershipfor progress. should facilitate this. The DuddonEstuary Partnership.

Disturbancemay also have an importanteffect on Bibby,C.J., Burgess,N.D. & Hill, D.A. 1992. Bird census techniques. Academic Press, London. breedingwaders, especiallyon the popularstretches of beach to the south and west of Askam and Millom. Callion,J.C. (ed.) 1989 - 1994. Birdsin Cumbda:a countynatural Relativelyfew walkers use the embankmentsand historyreport. CumbriaNaturalists' Union. saltmarshesin the northernhalf of the estuary, although Cook,A.S., O'Dowd,B. & Durdin,C.J. 1994. Breedingredshanks numbers may increasewith the recent developmentof the on Essexsaltmarshes in 1993. The Essex Bird Report 1993: CumbriaCoastal Way longdistance footpath, which 125-147. follows much of the shoreline. Use of the slagbanksat Askam and BorwickRails by dog walkers and anglers EnergyTechnology Support Unit 1994. DuddonEstuary Tidal EnergyBarrage Preliminary Feasibility Study. ETSU (some in cars) appearsto be increasing,and is likelyto T/06/001,44/REP. have an adverse effect on the productivityof Oystercatcher,Ringed Plover and Lapwing, as well as the Gibbons,D.W., Reid, J.B. & Chapman,R.A. 1993. The new atlas Little Tern Sterna albifronscolony at BorwickRails. of breedingbirds in B#tain and Ireland. Poyser,London. Hutcheson,M. (ed.) 1987, 1988. Bircisin Curnbda:a countynatural In the southand east of England,the large proportionsof historyreport. CumbriaNaturalists Union. the populationsof Oystercatchersand Ringed Plovers McAIone,D. (ed.) 1995. Birdsin Curnb#a:a countynatural history now nesting in nature reservesand protectedareas is report. CumbriaNaturalists Union. probablya result of intensiveuse of the seashore for recreation(Gibbons et aL 1•994). Densitiestherein may Murray,S, Hinds,P., Davenhill,A, Morris,S. & O'Brien,M. 1995o be h,gh; for example, Ringed Plovers nested at a density Numbersof lowlandbreeding waders •n northernEngland. of 40 pairs/km on the shingle islands in Langstone UnpublishedRSPB report. Harbour, Hampshire in 1984 and 1985 (Radford 1985a, O'Brien,M. 1994. Surveyof breedingwaders on Scottishlowlands. 1985b). Aroundthe DuddonEstuary, only the slagbankat UnpublishedRSPB report. Hodbarrowhas some degree of protectionfrom human O'Brien,M. 8, Smith, K.W. 1992. Changesin the status of waders disturbance. breedingon wet lowlandgrasslands in Englandand Wales between1982 and 1989. Bird Study 39:165-176. Piersma,T. 1986. Breedingwadersin Europe. Wader Study ACKNOWLEDGEMENTS Group Bulletin48, Supplement.

Grateful thanks are due to Peter , Peter Entwhistle, Prater,A.J. 1976. Breedingpopulation of the RingedPlover in Britain. Bird Study23: 155-161. Trevor Jones, Stephen Peter and Bob Treen for their efforts in the field, and also to Mark O'Brien and Lennox Prater,A.J. 1989. RingedPlover Charad#us hiaticula breeding Campbellfor their commentson this paper. populationof the UnitedKingdom in 1984. BirdStudy 36: 154- 159.

Radford,D.J. 1985a,b. LangstoneHarbour Reserve Annual REFERENCES Reportsfor 1984 and 1985. UnpublishedRSPB reports. Waters, R.J. & Cranswick,P.A. 1993. The WetlandBird Survey Allport,G., O'Brien,M. & Cadbury,C.J. 1986. Surveyofredshank 1992-93: wildfowl and wader counts. BTO/WWT/RSPB/ and otherbreeding birds on saltmarshesin B#tain, 1985. JNCC, Slimbridge. Nature ConservancyCouncil, CSD Report No 649, Peterborough. Batten•L.A., Bibby,C.J., Clement,P., Elliot,G.D. & Porter,R.F.

31