Seabird numbers and breeding success, 2006
Mavor, R.A., Heubeck., M. Schmitt, S. and Parsons,. M
UK Nature Conservation No 31
Observers at many seabird colonies throughout Britain reported a later than average breeding season in 2006.



Seabird numbers and breeding success


This is the eighteenth 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 2006 are summarised and compared with results from previous years, primarily 2005, with an analysis of longer term trends in the context of recent findings.


Some findings of particular note in 2006 are summarised below:


Observers at many seabird colonies throughout Britain reported a later than average breeding season in 2006.  Feeding conditions again appeared to be less than ideal, with most species probably affected by a shortage of food, especially during the latter stages of chick-rearing.


It was another late breeding season on Shetland for red-throated divers, where the number of pairs nesting was generally high, but success was below average. On Orkney, the number of pairs nesting was also high and they were more successful than average.  On Eigg, all nests again failed due to predation by otters.


Northern fulmar numbers decreased in Orkney and in western Britain between 2005 and 2006, but increased in Shetland and in eastern Britain. Overall, success was slightly below the UK and Ireland long-term mean.


Productivity of Manx shearwaters was below average at the few monitored colonies.  On Rum, it was the latest and most protracted breeding season since 1969.  Crows removed eggs from accessible burrows on Bardsey. A survey of European storm-petrel colonies on the Isles of Scilly found 1,398 AOS, similar to that recorded in 2000. Leach’s storm-petrel numbers on Dun, St. Kilda, were estimated at 13,523 AOS, similar to numbers in 2003, suggesting that the decline in the size of the UK’s largest colony had at least slowed.


After the decreases in 2005, in response to a late winter/early spring wreck, great cormorant and European shag numbers in many eastern regions increased, but decreases were noted in the west.  Breeding success of European shag was also higher than in 2005 in eastern regions, but not the west.


After a long period of decline, Arctic skua numbers in Shetland and Orkney increased for a second successive year. Breeding success in these regions was higher than in 2005, despite complete failures at some colonies, but was low in west Scotland. Great skua breeding success was higher than in 2005 too, particularly in Shetland.


Mediterranean gulls continued to increase, with at least 350 pairs fledging approximately 250 young.  Black-headed, common and lesser black-backed gulls also had a poor breeding season in 2006 with relatively few young fledged in many regions.  Mink activity at colonies in western Scotland was found to have reduced breeding success of common gulls by 75%, lesser black-backed gulls by 33% and herring gulls by 36%.


Black-legged kittiwake numbers decreased, or remained stable, in most regions although in SE England numbers were 70% higher than in 2005; the first increase detected there since 1995.  Breeding success was low, except in NE England. Pipefish were again a major component of food items brought back to the nest.


Sandwich tern numbers and breeding success were similar to 2005.  Roseate tern numbers were almost 20% higher than in 2005, due to a substantial increase at Rockabill, and productivity was high overall. Common terns had a better breeding season than in 2005, with higher numbers and breeding success in most regions.  Arctic terns suffered large declines in Scotland (except in Shetland) and breeding success for this species, and little tern, was high in Wales but generally poor elsewhere.  Presumed food shortages, predation, bad weather and tidal inundation were all factors which depressed tern breeding success in 2006.


Common guillemot numbers were mostly stable between 2005 and 2006, but declines occurred in a few western regions of Britain, and in NE Ireland.  Regional trends have been mostly positive since 1986 although declines have occurred in Scotland recently.  Mean productivity was, after 2004 and 2005, the third lowest recorded. Razorbill numbers in plots increased in Orkney, but decreased, or at least remained stable, in most regions since 2005. Whole-colony counts indicated increases in eastern regions, and in NW England, but numbers in most western regions declined.  For the third successive year mean breeding success was markedly lower than the long-term average.  Productivity was particularly low in colonies in the Northern Isles and Wales.


Black guillemot numbers in Shetland and Orkney were stable between 2005 and 2006.  However, numbers have halved in Orkney since 1986, although there has been virtually no change in numbers in Shetland over this time.  Atlantic puffin breeding success was near average in 2006. However, success was low on Fair Isle and St. Kilda, although at the last site productivity was double that of 2005, which was the worst season recorded there.


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 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 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.

Further information on Seabirds
ISBN 13 978 1 86107 605 2
ISSN 0963 8083
Please cite as: Mavor, R.A., Heubeck., M. Schmitt, S. and Parsons,. M, (2008), Seabird numbers and breeding success, 2006, UK Nature Conservation No 31, ISBN 13 978 1 86107 605 2, ISSN 0963 8083