Global warming - British birds nesting earlier, changing distribution

14/08/2008 20:42:33 Climate change is causing a number of widespread British birds to lay their eggs much earlier than 40 years ago, that's just one of the trends revealed in the latest State of the UK's Birds report - an annual publication produced by a coalition of conservation organisations looking at the fortunes of the UK's bird populations.

Information from the British Trust for Ornithology's Nest Record Scheme (incorporated in the State of the UK's Birds report for the first time) shows that birds like the chaffinch are, on average, laying their eggs about a week earlier than they did in the mid 1960s. Information obtained for other species, such as blue and great tits, robins and swallows, shows a similar pattern. The changes in laying dates recorded since the mid 1960s are believed to be in response to increasing temperatures triggered by climate change. In 1966, the average date for chaffinches laying their first egg was May 11, but by 2006 this date had moved forward to May 2. For robin, the average dates have moved from April 28 to April 22, in 2006.

30,000 nests monitored
Dr David Leech, organiser of the BTO's Nest Record Scheme, said: "Every year a network of 500 BTO volunteers monitor 30,000 nests, providing an enormous wealth of information about the changes in nesting activities of many of our birds. Over time, this body of information reveals a fascinating insight into how wildlife is affected by environmental changes."

Song thrushes - More chicks in wet summers
The report, which is produced by a partnership of organisations, also shows that birds are impacted by climate change in other ways too. Information from the British Trust for Ornithology shows that song thrushes rear fewer young during dry summers. Song thrushes feed their chicks largely on earthworms which are much harder to find in drier ground. A graph combining rainfall in England and Wales with song thrush nesting success showed that the birds reared more young than any year since 2004 - another wet summer. Drier summers are an anticipated feature of climate change in the UK (Not happening yet Ed.) and the data indicates that this bird of conservation concern will struggle in future.

Dunlin, autumn moult. Wasing at Snettisham RSPB reserve, Norfolk. Chris Gomersall (rspb-images.com)

Wading birds
Each winter the UK's food-rich estuaries are vital to the survival of internationally-important numbers of wading birds that arrive from northerly and easterly breeding grounds. Although the overall number of these birds increased by about 50 per cent up to the late 1990s, numbers have since started to decline. The declines have been particularly acute for several key species, including purple sandpipers, ringed plovers and dunlins. These waders have decreased by 59, 13 and 21 per cent respectively between 1979/90 and 2004/05 and this decline is largely thought to be fuelled by birds wintering elsewhere in Europe where conditions are becoming more suitable. The report confirms that the dunlin, which used to be the UK's most numerous wading bird in winter, is now at its lowest level since records began. Volunteers for the Wetland Bird Survey now count more knot than dunlin. However, in colder than average winters, the UK's estuaries will remain crucial for birds escaping harsher conditions in continental Europe.

Balearic shearwater
This year's report also looks at the plight of the Balearic shearwater - the only Critically Endangered bird to regularly visit the UK. A study reveals that one in 10 of the world population of this dove-sized relative of the albatross visits UK inshore waters. Breeding around Majorca and the other Balearic islands, this bird migrates out of the Mediterranean to the Atlantic during the autumn. Research has shown that the birds are having to travel increasingly further north in search of food because of shifts in the distribution of fish driven by climate change.

Dr Mark Avery, the RSPB's Conservation Director, said: "This year's report shows that climate change is with us already and from our gardens to our seas, birds are having to respond rapidly to climate change simply to survive. As often before - birds are acting like the canaries in a mine shaft and giving us early warning of dangerous change."

The State of the UK's Birds 2007 report is produced by a coalition of three NGOs - the RSPB, the British Trust for Ornithology and the Wildfowl & Wetlands Trust - and the UK Government's four statutory nature conservation agencies - the Countryside Council for Wales, Northern Ireland Environment Agency, Natural England and Scottish Natural Heritage.

The State of the UK's Birds series of reports was first published in 2000.