The number of finches in UK gardens was at their highest level for five years this winter following a shortage of food supplies in the wild, a survey revealed today.
But overall the number of birds seen in the RSPB's annual Big Garden Birdwatch has dropped by a fifth since 2004 because of milder winters and long term declines of some species.
Numbers of some of the most common bird species such as the house sparrow and starling have dropped dramatically over the 29 years the survey has been running, the RSPB said.
The 2008 study showed the yellow and black siskin has increased by almost two thirds since 2004 and was seen in three times as many gardens as last year. The small but striking member of the finch family has made it into the survey's top 20 for the first time, with large numbers driven from Scandinavia where conifer seed crops have been poor this year.
Numbers of the redpoll have rocketed since 2004 by 1,275%, and were seen in twice as many gardens as last year, again due to a lack of food in the wild.
The brambling - similar to the chaffinch - has also been seen in higher numbers because of poor crop of beech seeds or "mast" in northern Europe and Scandinavia, the RSPB said. And as expected, the goldfinch made it into the top 10 most commonly spotted birds for the first time, encouraged by warmer temperatures in the UK - and the trend for less manicured gardens.
The RSPB's Andre Farrar said milder winters meant the goldfinch was overwintering in the UK in larger numbers, At the same time British gardens are becoming a more welcoming place for them as homeowners put out seeds such as nyjer and leave patches for wild plants to grow which provide food, he said.
Dr Farrar said: "It's definitely been a good winter for finches. Many of them are here because of food supplies. Along with siskin increases, numbers of redpolls seen in gardens have skyrocketed.
"Both birds feed on conifers and deciduous seeds, so the figures suggest that tree seed supplies have been poor this year and they've been forced into gardens to find food."
The warmer temperatures mean the national survey, which took place over the weekend of January 26-27 this year and provides a snapshot of how the UK's birds are doing, is now almost a "spring" event rather than a winter one, Dr Farrar said. It does not mean there will not be cold snaps in the future which send birds "pouring" into gardens in search of food.
But the lower numbers in recent years are in part due to the absence of the kind of harsh weather once seen during the Birdwatch weekend, he said.
"These are very profound changes to our climate we are seeing. For the foreseeable future we're in a period when we've got much milder winters."
The changes in bird numbers, which saw an average of 28.4 birds per garden this year compared to an average of 34.8 per garden in 2004, are also in part due to declines in key species.
"Some of these species such as the house sparrow are subject to long term decline and there are fewer of them about since the survey started," Dr Farrar said.
Sparrow numbers have dropped 64% since the first Garden Birdwatch in 1979, although they are still the most frequently seen bird, while the second most common bird, the starling, has seen numbers plummet by 77% in that time.
The blackbird and chaffinch have seen numbers drop 39% and 28% respectively, but big winners have been the woodpigeon and collared dove which have seen numbers rise by 665% and 411%.
Numbers of the increasingly threatened song thrush have declined by 62.9% since 1979.
Almost 400,000 people spent an hour counting more than six million birds in their gardens or local parks in the Big Garden Birdwatch this January.