Last year's harsh winter hit Britain's smallest bird hard, with the number of gardens in which goldcrests were spotted falling by almost a half, according to the British Trust for Ornithology.
The declines in the tiny bird, which at just 6g weighs less than a 10p piece, were seen throughout the UK and Ireland as the region battled with the coldest winter for several decades.
Across the British Isles, goldcrests were seen in 48 per cent fewer gardens between January and March than on average, with declines reaching 60 per cent in Scotland, the South West and the east of England.
According to the British Trust for Ornithology, the reduction in the number of gardens where goldcrests were resident over the winter month was an "early warning" of possible major declines in the population as a whole - as gardens would be expected to be a refuge for the birds.
In winter, they visit gardens in larger numbers to feed on fat-based foods put out by householders, and in the unusually snowy and icy conditions which gripped the UK and Ireland earlier this year they would be expected to be seen in more gardens.
The BTO warned the declines in goldcrests in gardens between January and March, observed by people taking part in its year-round weekly Garden BirdWatch, suggest a crash in the population at large.
Tim Harrison, of BTO Garden BirdWatch, said goldcrests were not able to carry much in the way of food reserves and as a result were vulnerable to starvation.
Because they are so small - at just 9cm long - they also run a higher risk of becoming chilled, he added.
And he said: "Particularly during very cold weather you would expect gardens to be a refuge for lots of birds including goldcrests.
"So the fact that numbers have been particularly low in gardens suggests that, because they might be a preferable habitat, what is happening in gardens is going to be reflective of what's happening to the population in all habitats. "This is an early warning that we suspect there could be a distinct downward trend in terms of the wider population."
He said numbers were considerably lower this winter because of the cold weather and because fewer goldcrests came into the UK from other parts of Europe during the autumn.
Other small birds also suffered in the face of the cold weather, with tiny wrens seen in 22 per cent fewer gardens than over the long-term average from 1995 to 2009, and treecreepers spotted in 15 per cent fewer backyards.
Dr Harrison added: "The goldcrest is a 'boom and bust' species - after cold winters only a quarter of the autumn population may be left to breed, but numbers can rally with pairs sometimes rearing more than 15 chicks in the following spring and summer.
"It remains to be seen how the population will shape up after the current breeding season."
Monitoring by the BTO over the breeding season will reveal if the goldcrest has managed to be more productive this spring, enabling numbers to bounce back, he said.