The Impact of the Sea Empress Oil Spill on Birds of The
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THE IMPACT OF THE SEA EMPRESS OIL SPILL ON BIRDS OF THE PEMBROKESHIRE COAST AND ISLANDS Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1997/1/217/2351515/2169-3358-1997-1-217.pdf by guest on 30 September 2021 Stephen J. Parr, Robert J. Haycock, and Malcolm E. Smith Countryside Council for Wales Pias Penrhos Bangor, Gwynedd LL57 2LQ United Kingdom ABSTRACT: Much of the Pembrokeshire coast and islands, together sequently a second group of medium- to longer-term "impact" projects with its inshore waters, are of international importance for their breed- were instigated to measure the ongoing effects on birds, especially on ing seabirds and wintering seaduck. Although the Sea Empress oil spill breeding seabird populations. A third group of projects relating to the occurred before the breeding season, some 7000 oiled birds were recov- separate issue of the welfare of oiled birds are classified as "rehabilita- ered dead or alive. The impact of the oil spill on birds can be classified tion" projects. Hence the structure of this paper reflects this temporal as follows: immediate mortality especially of more than 4500 wintering change in project type and the separate issue of rehabilitation. Since the common scoter in Carmarthen Bay; sublethal effects on productivity of outputs from most of the impact projects are still due, this must remain colonies and reduced adult survival from oil or dispersant Ingestion; a provisional assessment until all the results are available. Much of these and chronic effects on bird populations from long-term pollution, par- data will be provided as an update at the conference. ticularly of prey. A range of monitoring and research projects are under way to investigate the impact, but it is premature to provide many results. The oil spill probably caused significant local declines in seabird colony sizes, especially of guillemot. The impact on common Reaction to the oil spill scoter will prove difficult to determine because of the poor quality and high variability of preincident data. Large numbers of oiled birds, par- Following the grounding on February 15, 1996, an immediate bird ticularly common scoter, were treated and subsequently released. The casualty monitoring program was established along the Pembrokeshire successful rehabilitation of such released birds is controversial; coastline. Data were also collated from other important seabird areas research and review results will be reported. affected, including Lundy Island, the North Devon coast, and southeast Ireland. Numbers of casualties were logged, and, where possible, dead birds were retrieved and frozen for further research. Coordinated ground-based surveillance of birds and collection of oiled bird casual- ties continued almost daily between February 16 and March 31 over an On February 15, 1996, the Sea Empress ran aground off St. Anne's extensive shoreline. Thereafter occasional surveys were made of Head, at the mouth of Milford Haven in Pembrokeshire, southwest selected areas of the coastline in April and May. Aerial surveys of Wales. Up until February 21 she discharged 72,000 tons of crude oil and coastal waters, particularly Carmarthen Bay and around Skomer and 360 tons of heavy fuel oil into the sea. As part of the cleanup operation, Skokholm, were conducted daily between February 20 and March 7. 445 tons of dispersant and 8 tons of demulsifier were aerially sprayed Provisional identification of casualties up to June 1,1996, indicates that on the larger patches of oil (SEEEC, 1996). The most heavily oiled some 6935 birds of at least 28 species were recovered dead or alive stretches of coast included much of Milford Haven, the Castlemartin (Table 3). Oiled bird casualties were reported from February 17 coast, St. Margaret's and Caldey islands, and the west end of Carmarthen onwards. Small numbers were still being found during May, but the Bay (Figure 1). peak numbers, about 85% of the dead and rescued birds, were recorded The Pembrokeshire coast and particularly the islands, together with between February 24 and March 4, 1996 (Figure 3). its inshore waters, are of international importance for their breeding Seabirds. Dead and live oiled seabirds were recovered from many seabirds, wintering seaduck, and wintering waterfowl (Table 1). The mainland beaches. The majority were found along the south Pem- affected area supports approximately half a million breeding seabirds, brokeshire and Carmarthenshire coastline (see Table 3). Over 1900 including 50% of the U.K. population of Manx shearwater (Puffinus (28%) of bird casualties were guillemot {Uria aalge), and 66% of the puffinus), the fourth largest gannetry {Morus bassanus) in the world, and dead oiled auks recovered were found between Linney Head and Tenby, 40,000 auks, principally on Skomer and Skokholm (Lloyd et al, 1991). close to the important seabird colonies at Elegug Stacks (Castlemartin In winter it supports over 40,000 wintering waterfowl, including up to coast), Stackpole Head, and St. Margaret's Island. Bird casualty figures 30% of the U.K. common scoter (Melanitta nigra) wintering population, reported from the main seabird colonies on the islands of Skomer, in Carmarthen Bay (Stewart, 1995). Consequently the area is unusually Skokholm, and Ramsey were small, but nonetheless 155 oiled bird rich in European Union (EU) and U.K. site protection designations corpses were found on the adjacent mainland between the mouth of Mil- (Figure 2). However, both Ramsey and St. David's Peninsula Coast and ford Haven and St. Brides Bay, most of which were auks. Castlemartin Coast Special Protection Areas (SPAs) are designated Offshore boat surveys, following standard transect methods, were under the EU's Wild Birds Directive solely for their chough Pyrrho- conducted between February 25 and 29 at the time of peak corpse corax pyrrhocorax populations and not for seabirds. retrieval from beaches (see Figure 3). This provided data on seabird den- The initial priority as a result of the spill was to count and collect dead sities. A mean density of 3.4 birds/km2 (of 15 species) was recorded and oiled birds and to monitor the effect of the oil on birds at sea. These within a 4% sample of a 5500-km2 total sea area. This suggests that there projects were classified as short-term "reaction" projects (Table 2). Sub- were approximately 20,000 seabirds in offshore waters. There was no 217 Key ■H Site of Special Scientific interest ■B Special Protection Area ! Γ7771 Proposed Special Protection Area Figure 2. Distribution of Special Protection Areas and Sites of Special Scientific Interest in southwest Wales Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1997/1/217/2351515/2169-3358-1997-1-217.pdf by guest on 30 September 2021 September 30 on guest by http://meridian.allenpress.com/iosc/article-pdf/1997/1/217/2351515/2169-3358-1997-1-217.pdf from Downloaded 1997 INTERNATIONAL OIL SPILL CONFERENCE 219 Table l. Important concentrations of breeding and wintering birds in southwest Wales Site name Criteria, Species Abundance? Skomer SPA Manx shearwater Pujfinus puffinus 150,000 Fulmar Fulmarus glacialis 700 Storm petrel Hydrobates pelagicus 100 Great black-backed gull Larus marinus 60 SPA Lesser black-backed gull Larus fuscus 15,500 Herring gull Larus argentatus 450 Kittiwake Rissa tridactyla 2,300 SSSI Guillemot Uria aalge 10,0001 SSSI Razorbill Alca tor da 3,3001 Downloaded from http://meridian.allenpress.com/iosc/article-pdf/1997/1/217/2351515/2169-3358-1997-1-217.pdf by guest on 30 September 2021 SSSI Puffin Fratercula arctica 10,5001 Middleholm Manx shearwater Pujfinus pujfinus 2,000 Shag Phalacrocorax aristotelis 25 Razorbill Alca torda 200 Puffin Fratercula arctica 200 Skokholm SPA Manx shearwater Pujfinus pujfinus 40,000 Fulmar Fulmarus glacialis 150 SPA Storm petrel Hydrobates pelagicus 4,000 Great black-backed gull Larus marinus 40 SSSI Lesser black-backed gull Larus juscus 3,000 Herring gull Larus argentatus 400 SSSI Razorbill Alca torda 9001 SSSI Puffin Fratercula arctica 2,7001 Grassholm SPA Gannet Morus bassanus 33,000 Guillemot Uria aalge 700 Ramsey and Bishops and Clerks Fulmar Fulmarus glacialis 250 Storm petrel Hydrobates pelagicus 200 Lesser black-backed gull Larus juscus 250 Herring gull Larus argentatus 150 Kittiwake Rissa tridactyla 500 Guillemot Uria aalge 2,5001 SSSI Razorbill Alca torda 1,2501 SPA Chough Pyrrhocorax pyrrhocorax Stackpole Head and Castlemartin Kittiwake Rissa tridactyla 400 Guillemot Uria aalge 6,750 I Razorbill Alca torda 6001 SPA Chough Pyrrhocorax pyrrhocorax 12 St. Margaret's Island Cormorant Phalacrocorax carbo 200 Shag Phalacrocorax aristotelis 20 Guillemot Uria aalge 8001 Razorbill Alca torda 2001 Caldey Lesser black-backed gull Larus juscus 400 Herring gull Larus argentatus 1,400 Milford Haven and Cleddau estuary (winter) SSSI Total wildfowl 4,050 SSSI Total waders 7,100 Total gulls 4,700 Carmarthen Bay (winter) Red-throated diver Gavia stellata 100 Cormorant Phalacrocorax carbo 250 SPA Common scoter Melanitta nigra Max 25,000 Total breeding birds 485,330 Total wintering birds 41,200 I = individuals; otherwise abundance measured in pairs. 1. SPA: > 1% of UK breeding population of species on Annex 1 of the EU 'Birds' Directive 1979, hence site of international importance and desig- nated as Special Protection Area. SSSI: > 1% of U.K. breeding population, hence site of national importance and notified as Site of Special Scientific Interest. 2. From Seabird Colony Register of the Joint Nature Conservation Committee and Lloyd et al. (1991). apparent relationship between the numbers of guillemots and razorbills Ireland, where some 362 dead oiled birds, mainly auks, were reported (Alca torda) recorded in coastal waters and the numbers recorded dead from mid-March onward, including a high proportion of guillemot (see on adjacent coasts. A corpse-drift experiment was also conducted off the Table 3). Computer modeling of corpses and oil dispersal suggests that south Pembrokeshire coastline in early March to try to determine the both traveled south toward Devon and Cornwall before being blown recovery rate of birds that died at sea.