Many British birds are laying their eggs earlier in the year as a result of climate change, a report by conservation groups claimed yesterday.

The report said birds were being forced to rapidly adapt their behaviour in order to survive, including altering their nesting and migration patterns and travelling further to find food.

Work carried out by the British Trust for Ornithology (BTO) surveying 30,000 nests showed species such as the chaffinch and robin are laying their eggs about a week earlier than they did during the 1960s.

A similar pattern has been observed for other species such as blue and great tits and swallows.

There are concerns that disruption of the natural patterns in the birds' egg-laying could mean they are out of sync with the emergence of the food sources on which they feed their young, such as caterpillars.

Matt Murphy, ornithologist for the Countryside Council for Wales, said climate change was affecting the breeding patterns of pied flycatchers living in Welsh oak woodlands.

In Scotland there has been a fall in the breeding success of seabirds such as guillemots, puffins and kittiwakes as warming sea temperatures affect the food chain. Conservationists are concerned the decrease, the result of a lack of sand eels, will mean fewer breeding birds and continued decline of key species.

Another seabird, the critically endangered Balearic shearwater, has been seen increasingly in the UK as the impact of climate change on fish is forcing it to migrate up to 20% further in search of food.

Dr Mark Avery, conservation director for the RSPB, one of the groups involved in the study, 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 report also said many of the UK's farmland and woodland bird species were continuing to decline, particularly those specialists which require a particular habitat such as the lesser-spotted woodpecker.

Other species have stabilised after huge falls since the 1970s.

Some have increased their numbers, including the tree sparrow and reed bunting, after suffering severe declines.