Global warming brings an early laying season for Britain's birds

Climate change is causing familiar British birds to lay their eggs earlier, according to a survey of UK bird populations.

Species like the chaffinch are laying their eggs about a week sooner than 40 years ago and blue tits, great tits, robins and swallows arebehaving in a similar fashion, the State of the UK's Birds report for 2007, published today, has found.

In 1966, the average date for chaffinches laying their first egg was 11 May, but it was 2 May in 2006. For the robin, the date has moved from 28 April to 22 April. The Nest Record Scheme of the British Trust for Ornithology (BTO) revealed the changes, which are believed to be a response to increasing temperatures.

The annual survey highlights a number of shifts in bird behaviour thought to be related to climate change.

A group of conservation organisations produces the report, including the BTO, the Royal Society for the Protection of Birds (RSPB) and the Wildfowl & Wetlands Trust.

The report also found numbers of wading birds wintering in British estuaries after breeding in the High Arctic and Russia have declined. The overall number increased by about 50 per cent up to the late 1990s, but numbers are falling.

The declines have been particularly acute for several key species including purple sandpipers, ringed plovers and dunlins, whose populations decreased by 59, 13 and 21 per centrespectively in the 25 years to 2004-05.

These declines are largely thought to be fuelled by birds wintering elsewhere in Europe, where rising temperatures are making conditions more suitable.

The report confirms that the dunlin population, which used to be the most numerous winter wading bird in the UK, is now at its lowest level since records began.

However, in colder than average winters, the report points out, British estuaries will remain crucial for birds escaping harsher conditions on the continent.

The report also found song thrushes were rearing fewer young in dry summers. The birds use wet areas like ponds and ditches to find food, but these are in decline, meaning the birds struggle to feed their young in dry summers.

Dr Mark Avery, the RSPB conservation director, said climate change had already begun. "From our gardens to our seas, birds are having to respond rapidly to it simply to survive."