Breeding Waders Around the Duddon Estuary in 1994
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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 North Walney 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-Furness 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- Walney Island 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.). Millom 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 United Kingdom 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) Cumbria 1993 3.0 0.2 2.8 0•1 about three-quartersof the estuary population. Numbers (randomsites) breedingin Englandand Wales increasedby 20% Lancashire 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,