Continuing pressures on seabirds

The latest results from the Seabird Monitoring Programme (SMP) have been published online.

Established in 1986 the Seabird Monitoring Programme is an annual review of the 25 species of seabird that regularly breed in Britain and Ireland. Co-ordinated by JNCC in partnership with other environmental and conservation organisations data on numbers and breeding success are collected to assess the species conservation status both regionally and nationally.

The main findings from the latest report are that between 2000 and 2010 the UK abundance index of four species decreased by greater than 30% – Arctic skua (-34%), black-legged kittiwake (-30%), lesser black-backed gull (-36%) and herring gull (-38%). Only roseate tern (+99%) increased by greater than 30%.

Reasons for these declines vary. For Arctic skua, factors include competition for nesting territories with great skuas, which have increased markedly, and reductions in sandeel stocks. Declines in sandeel abundance also impacted on black-legged kittiwake populations; productivity and adult survival have been negatively affected by the presence of a sandeel fishery that operated off SE Scotland. In certain regions productivity and survival of black-legged kittiwakes is negatively linked with sea surface temperatures, which have risen due to climate change. 

Fisheries also impacted on herring and lesser black-backed gulls. The latter species increased until around 1993, probably as a result of increased food availability from fishery discards and from landfill sites. Causes of recent decreases are unknown, although these may be a reverse of the factors responsible for earlier increase. Reasons for decline in the herring gull are not fully known, but botulism caught from refuse tips may have been a factor. Decreases in the availability of food scavenged from refuse tips and reductions in discards from fisheries may also have played a role. Numbers of both these gulls have been increasing in urban areas, a much talked about problem, due to an easy supply of available food (e.g. from fast-food and domestic/commercial rubbish bins), and safe (predator-free) nesting sites. However, these increases do not compensate for losses recorded at natural sites.

The increase in roseate tern numbers follows a severe decline partly caused by mortality of immature birds on their W African wintering grounds (caught for food/sport). From 1991, the population in England increased caused in part by reduced pressure in Africa following an education campaign, and by conservation measures which include provision of nest boxes and habitat management. The Scottish population, numbering about 33 pairs in mid 1980s, has fallen almost to zero. Competition with and predation by gulls are thought to be responsible.

The current report, the second produced online, replaces and builds upon the previous Seabird numbers and breeding success in Britain and Ireland publication. Improved study methods and in-house designed software has led to easy, quick and versatile analysis of seabird colony data which can be tailor-made for a variety of projects.  The data have contributed to marine assessments including Charting Progress 2 and the State of Scotland’s Seas. Data are also used as part of headline indicators relating more widely to the status of UK bird populations as part of measuring progress towards EU and CBD targets. Furthermore, the data also form an important component of one of the UK headline indicators for sustainable development as well as being part of the bird indicators on the Biodiversity Action Plans in England and Scotland.