UK Nature Conservation No. 28 Seabird numbers and breeding success in Britain and Ireland, 2003 R.A. Mavor, M. Parsons, M. Heubeck and S. Schmitt Roddy Mavor and Matt Parsons, Seabirds and Cetaceans, Joint Nature Conservation Committee, Dunnet House, 7 Thistle Place, Aberdeen, AB10 1UZ Martin Heubeck, Shetland Oil Terminal Environmental Advisory Group, Department of Zoology, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB9 2TN Sabine Schmitt, Research Department, Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire, SG19 2DL Cover painting of black-legged kittiwakes by David Bennett. Cover design by Green Associates, 1994. Further information on JNCC publications can be obtained from: JNCC, Monkstone House, City Road, Peterborough PE1 1JY Published by Joint Nature Conservation Committee, Peterborough Copyright: Joint Nature Conservation Committee 2004 ISBN 1 86107 564 2 ISSN 0963 8083 Seabird numbers and breeding success, 2003 This report should be cited as follows: Mavor, R.A., Parsons, M., Heubeck, M. and Schmitt, S. 2004. Seabird numbers and breeding success in Britain and Ireland, 2003. Peterborough, Joint Nature Conservation Committee. (UK Nature Conservation, No. 28.) Original data from the report may not be used in other publications (although general results and conclusions may be cited) without permission of JNCC, RSPB and/or SOTEAG, as relevant. Requests to use data should be channelled through S. Schmitt/RSPB (petrels, terns and skuas), M. Heubeck/SOTEAG (cliff-breeding species and black guillemots in Shetland) or Roddy Mavor/JNCC (other species/regions). Where necessary, such requests will be forwarded to other contributing organisations or individuals. 2 Contents Contents Page no. Summary 4 1 Introduction 5 1.1 The Seabird Monitoring Programme and Seabird Colony Register 5 1.2 Data presentation and methods 6 2 General features of the 2003 breeding season 12 3 Species accounts 13 3.1 Red-throated diver Gavia stellata 13 3.2 Northern fulmar Fulmarus glacialis 15 3.3 Manx shearwater Puffinus puffinus 20 3.4 European storm-petrel Hydrobates pelagicus 21 3.5 Leach's storm-petrel Oceanodroma leucorhoa 21 3.6 Northern gannet Morus bassanus 22 3.7 Great cormorant Phalacrocorax carbo 24 3.8 European shag Phalacrocorax aristotelis 29 3.9 Arctic skua Stercorarius parasiticus 34 3.10 Great skua Stercorarius skua 36 3.11 Mediterranean gull Larus melanocephalus 39 3.12 Black-headed gull Larus ridibundus 40 3.13 Mew gull Larus canus 42 3.14 Lesser black-backed gull Larus fuscus 44 3.15 Herring gull Larus argentatus 47 3.16 Great black-backed gull Larus marinus 50 3.17 Black-legged kittiwake Rissa tridactyla 53 3.18 Sandwich tern Sterna sandvicensis 62 3.19 Roseate tern Sterna dougallii 66 3.20 Common tern Sterna hirundo 68 3.21 Arctic tern Sterna paradisaea 73 3.22 Little tern Sterna albifrons 77 3.23 Common guillemot Uria aalge 82 3.24 Razorbill Alca torda 88 3.25 Black guillemot Cepphus grylle 92 3.26 Atlantic puffin Fratercula arctica 93 4 Acknowledgements 96 5 Bibliography 97 5.1 References used in this report 97 5.2 Recent publications relevant to breeding seabirds in Britain and Ireland 100 3 Seabird numbers and breeding success, 2003 Summary This report presents the results of monitoring of seabird populations and breeding performance throughout Britain and Ireland in 2003 and makes comparisons with previous years. The report is produced annually as part of the JNCC's Seabird Monitoring Programme, in collaboration with the Royal Society for the Protection of Birds (RSPB) and the Shetland Oil Terminal Environmental Advisory Group (SOTEAG). Some findings of particular note in 2003 are summarised below: • Fewer red-throated divers nested in Shetland in 2003 than in 2002 and did so later, possibly due to food shortages early in the season, but those that nested were quite successful. In Orkney breeding numbers were similar to 2002 and success was above average at all sites. • A survey of Leach’s storm petrels on Dun, St Kilda, revealed an apparent 48% decline in breeding numbers since it was last surveyed, in 1999, when it held 27,700 AOS to just 14,417 AOS in 2003. Predation of petrels by great skuas, whose population on St Kilda has increased dramatically, is known to be intense and the interactions between these two species is the subject of current research. • Two new breeding colonies of northern gannet were established in 2003, in Orkney: at Sule Skerry and at Noup Head, Westray. • Large increases in the breeding number of European shags were recorded in SE Scotland and NE England between 2002 and 2003, where numbers are now beginning to return to levels recorded prior to the ‘wreck’ in 1994. Long-term declines continue in NW Scotland and Shetland. • Overall, the population of Arctic skuas decreased by c.15% compared with 2002, to its lowest level since 1989. The decline was highest on Shetland, where many sites had their least productive year on record, caused by a severe lack of sandeels. Breeding numbers of great skuas were generally more stable, although breeding success was very low in Shetland. • Many of the larger breeding colonies of lesser black-backed gulls declined between 2002 and 2003. Numbers on Skomer and Skokholm were the lowest during the history of the SMP and numbers declined at major colonies in NW England, including S. Walney and Rockcliffe Marsh. • The long term decline in breeding numbers of black-legged kittiwake continued in 2003 in Shetland, SE Scotland and SE England. The population on Orkney appears to have stabilised, following declines during the 1990s. Near breeding failure occurred in Shetland. Productivity was higher in Orkney but well below 2002 levels. • Numbers of roseate terns reached their highest level since 1979, largely attributable to an increase on Rockabill (SE Ireland). However, fewer sites reported breeding than in any year since 1969. The 2003 breeding season was the most productive for 11 years. • Numbers of common guillemots generally decreased between 2002 and 2003, particularly so in Shetland, also in Orkney between 2000 and 2003. Increases occurred in SE Scotland (whole colony counts only), NE England and in Irish Sea colonies. Productivity generally declined between 2002 and 2003, reaching its lowest ever level in Shetland; some colonies in Orkney were similarly unproductive. • Large increases in breeding numbers of Atlantic puffin were noted in some of the larger colonies in SE Scotland and NE England, but declines also occurred in these regions. Many of the monitored colonies in the west of Britain decreased. Breeding success was higher than the long- term average in 2003. 4 Introduction 1 Introduction This is the fifteenth annual report on the results of seabird monitoring at colonies throughout Britain and Ireland, produced jointly by JNCC, RSPB and SOTEAG, as part of JNCC's Seabird Monitoring Programme. Available data on seabird breeding numbers and breeding success at seabird colonies in 2003 are summarised and compared with results from previous years, primarily 2002, with an analysis of longer term trends in the context of recent findings. The information contained in this report has been collated from many sources. These include research staff and wardens from a variety of organisations including RSPB, SOTEAG, JNCC, Scottish Natural Heritage, English Nature, Countryside Council for Wales, Irish National Parks and Wildlife Service, the Wildlife Trusts, bird observatories, National Trust and National Trust for Scotland, the Centre for Ecology and Hydrology and BirdWatch Ireland. Many dedicated fieldwork volunteers also contribute valuable data to the Seabird Monitoring Programme; refer to the Acknowledgements section for details. One aim of the annual report is to draw attention to notable changes in seabird numbers or breeding performance, which may merit direct conservation action or further research. It is also intended to provide feedback and, we hope, encouragement for future work, to the many individuals and organisations contributing data, by placing results for individual colonies or regions in a wider context. The results presented refer mainly to coastal or island populations of seabirds, but reference is also made to inland populations of great cormorants, gulls and terns where data are available. Any comments on this report, or offers of help for future years, would be greatly appreciated by the authors. We are also keen to receive any existing additional informati on numbers or breeding success for any seabird species, whether at coastal or inland colonies, which may not have been previously submitted to the Seabird Monitoring Programme. Any such data will be added to the long-term seabird databases maintained by JNCC and RSPB, including the JNCC/Seabird Group's Seabird Colony Register. Details of recommended methods for assessing seabird numbers and breeding success are given in the Seabird monitoring handbook for Britain and Ireland (Walsh et al. 1995). Copies of the Handbook, or other advice on seabird monitoring methodology, may be obtained from the Seabirds and Cetaceans Unit of JNCC at the address given on the title page. 1.1 The Seabird Monitoring Programme and Seabird Colony Register The JNCC's Seabird Monitoring Programme facilitates the co-ordination of seabird monitoring on a UK-wide basis. The aim of the programme is to ensure that sufficient data on breeding numbers and breeding success of seabirds are collected both regionally and nationally to enable their conservation status to be assessed. The programme assists JNCC, RSPB and partner organisations, including the statutory country nature conservation agencies, to monitor aspects of the health of the wider marine environment and to provide sound advice relevant to the conservation needs of breeding seabirds. Seabird monitoring directly funded by JNCC focuses particularly on species such as northern fulmar, European shag, black-legged kittiwake and auks, for which changes in breeding populations, breeding success or other parameters may provide evidence of changes in the marine environment as a whole.