Britain's smallest bird, the tiny goldcrest, may have suffered a population crash after being hit extremely hard by the harsh conditions of last winter, the British Trust for Ornithology (BTO) said yesterday.
Confirming fears that the species, which had been increasing in number because of the warmer winters of the past two decades, would suffer a serious reverse in the freeze, the BTO said the number of gardens in which goldcrests were spotted had fallen by almost half.
Across the British Isles, the tiny birds, which, at just 6g each, weigh less than a 10p piece, 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.
The reduction in the number of gardens where goldcrests were resident over the winter months was an "early warning" of possible major declines in the population as a whole, the BTO said.
In winter, goldcrests 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 declines, observed by people taking part in its year-round weekly Garden BirdWatch, suggest a crash in the population at large, the BTO warned.
Dr Tim Harrison, of Garden BirdWatch, said goldcrests were not able to carry much in the way of food reserves and were vulnerable to starvation. Because they are so small – just 9cm (3.5in) long – they also run a higher risk of becoming chilled, he added.
Other small birds also suffered in 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."