A number of UK bird species are laying eggs significantly earlier than they were 40 years ago, a report reveals.
A conservation coalition's report says some finches, robins and tits are all laying earlier and puts this down to warming caused by climate change.
Overall, numbers of farmland birds remain about half of what they were in the 1970s, while wintering populations of water birds have risen considerably.
The RSPB said birds were having to respond to climate change to survive.
The State of the UK's Birds report is produced annually by a coalition of conservation groups.
It includes the British Trust for Ornithology (BTO), the Royal Society for the Protection of Birds (RSPB) and the Wildfowl and Wetlands Trust (WWT), as well as the government agencies responsible for nature conservation in the UK's four national regions.
This body of information reveals a fascinating insight into how wildlife is affected by environmental changes
David Leech, BTO
"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," said Dr Mark Avery, the RSPB's conservation director.
"As often before, birds are acting like the canaries in a mine shaft and giving us early warning of dangerous change."
The report shows that on average, chaffinches are laying nine days earlier than in the 1960s, and robins six days earlier.
Chaffinches are among the birds found to be nesting earlier
Blue tits and great tits are among the other species displaying what scientists term a "phenological shift".
This response to rising temperatures has been documented in birds, insects, plants and mammals across a range of continents, and it is no surprise that the UK's birds should be changing their habits too.
In some species, the shift has been shown to be damaging, as it means key foods are no longer available when the youngsters need them.
But in other situations - as documented recently with English great tits - the wildlife appears to cope.
However, seabirds around the UK's northern shores have not been coping with drastic declines in prey such as sandeels in recent years, a consequence of industrial fishing and climate change.
This has brought abrupt local collapses of some colonies of species such as puffins and terns; but overall, the report shows, seabird numbers are still significantly higher nationwide than they were 30-40 years ago.
However, the UK is apparently losing other water birds including waders such as dunlins, ringed plovers and purple sandpipers.
Their numbers may actually be falling, perhaps through a climatic shift; or they may be wintering in other parts of Europe.
"The rate of redistribution of some water birds has been dramatic in recent years, but for some species we still know little about the extent to which decreases in numbers in the UK are due to redistribution to other parts of their range or real decreases in overall numbers," said Richard Hearn, water bird monitoring programme manager at the Wildfowl & Wetlands Trust.
The wet 2007 summer was a boon to song thrushes
"It is vital that we learn more about the extent and consequences of redistribution in order to ensure that these species are effectively conserved".
Also of concern will be the continued absence of a widespread recovery of farmland birds despite the introduction of various "agro-environmental schemes" designed to preserve and restore key habitat.
The data included in the annual surveys is largely gathered by volunteers, and the BTO's David Leech paid tribute to their efforts.
"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," he said.
"Over time, this body of information reveals a fascinating insight into how wildlife is affected by environmental changes."
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