UK Nature Conservation No. 27 Seabird numbers and breeding success in Britain and Ireland, 2002 R.A. Mavor, M. Parsons, M. Heubeck, G. Pickerell 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 Georgina Pickerell, 4, Sandy Road, Willington, Bedfordshire 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 2003 ISBN 1 86107 551 0 ISSN 0963 8083 Seabird numbers and breeding success, 2002 This report should be cited as follows: Mavor, R.A., Parsons, M., Heubeck, M., Pickerell, G. and Schmitt, S. 2003. Seabird numbers and breeding success in Britain and Ireland, 2002. Peterborough, Joint Nature Conservation Committee. (UK Nature Conservation, No. 27.) 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 Seabird numbers and breeding success, 2002 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 2002 breeding season 12 3. Species accounts 14 3.1 Red-throated diver Gavia stellata 14 3.2 Northern fulmar Fulmarus glacialis 16 3.3 Manx shearwater Puffinus puffinus 21 3.4 European storm-petrel Hydrobates pelagicus 22 3.5 Leach's storm-petrel Oceanodroma leucorhoa 23 3.6 Northern gannet Morus bassanus 23 3.7 Great cormorant Phalacrocorax carbo 24 3.8 European shag Phalacrocorax aristotelis 28 3.9 Arctic skua Stercorarius parasiticus 32 3.10 Great skua Catharacta skua 34 3.11 Mediterranean gull Larus melanocephalus 36 3.12 Black-headed gull Larus ridibundus 37 3.13 Mew gull Larus canus 40 3.14 Lesser black-backed gull Larus fuscus 41 3.15 Herring gull Larus argentatus 44 3.16 Great black-backed gull Larus marinus 47 3.17 Black-legged kittiwake Rissa tridactyla 49 3.18 Sandwich tern Sterna sandvicensis 58 3.19 Roseate tern Sterna dougallii 62 3.20 Common tern Sterna hirundo 64 3.21 Arctic tern Sterna paradisaea 69 3.22 Little tern Sterna albifrons 74 3.23 Common guillemot Uria aalge 78 3.24 Razorbill Alca torda 82 3.25 Black guillemot Cepphus grylle 86 3.26 Atlantic puffin Fratercula arctica 88 4. Acknowledgements 91 5. Bibliography 92 5.1 References used in this report 92 5.2 Recent publications relevant to breeding seabirds in Britain and Ireland 95 3 Seabird numbers and breeding success, 2002 Summary This report presents the results of monitoring of seabird populations and breeding performance throughout Britain and Ireland in 2002 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 2002 are summarised below: S Numbers of breeding red-throated divers were similar to those recorded in 2001. Breeding success in Shetland was higher than in 2001, while in Orkney it was lower than in 2001; in both regions success was above the long term average. S Few data were received on Manx shearwater in 2002. Breeding success on Rum was the highest since 1997, while further confirmation was obtained of the species’ demise on Canna. Productivity was high on Bardsey but again low on Skomer (although around average for the colony). S Numbers of European shag nests generally increased or remained stable in 2002, compared with 2001, except in Shetland, north-west Scotland and north-east England, where numbers at monitored colonies declined. The important colony on Canna was smaller than at any time since 1986 and productivity there was low. Fair Isle, Isle of May and Bardsey recorded their most productive seasons, Sumburgh Head its second most productive. S The recorded number of breeding Mediterranean gull fell between 2001 and 2002, due partly to an incomplete count of one of the larger colonies and to a high proportion of non-breeding at the large Langstone Harbour colony, probably caused by low food availability. The species bred successfully in Northern Ireland for the first time. S An ongoing study in western Scotland provided further information on the effect of mink predation on the productivity of gulls: breeding success was reduced by a mean of 44% in herring gulls and 57% in mew gulls over the last 6-7 years S Surveys of several large colonies of Atlantic puffin were undertaken in 2002. Numbers declined at Hermaness, increased on Coquet and remained stable on North Rona and Lunga (compared with surveys in 1997, 2001, 1993 and 2001, respectively). Successful breeding was confirmed on Ailsa Craig for the first time in decades following the eradication of rats in the early 1990s. S As in 2001, several species in Shetland had a poor breeding season in 2002, largely attributed to reduced availability of sandeels, although food appeared to be abundant for Orkney breeders. Both great skua and Arctic skua numbers declined (whereas in Orkney they increased) and productivity of great skuas on Fair Isle was the lowest on record and low at other Shetland colonies. Numbers of breeding black-legged kittiwakes continued to decline: the number within 18 colonies decreased by 39.6% between 1999 and 2002 and productivity was again low, with failures largely occurring at the egg stage. Arctic terns had a very unproductive season in 2002, yet birds on Orkney had their most successful season on record. Counts of common guillemots at study plots in Shetland (except Fair Isle) showed marked declines between 2001 and 2002 and the population index for the region was equal to the lowest recorded during the duration of the SMP. Productivity and weights of chicks at Sumburgh Head were low. 4 Seabird numbers and breeding success, 2002 1 Introduction This is the fourteenth 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 2002 are summarised and compared with results from previous years, primarily 2001, with an analysis of longer term trends in the context of recent findings. This edition of the report contains modest changes to the presentation of some of the information, which it is hoped will improve the readability of the report and assist in understanding the data; a description of the changes is given in section 1.2.5. 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 seasons, would be greatly appreciated by the authors. We are also keen to receive any existing additional information 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.