The increasing popularity of garden bird feeding may be helping the spread of a parasitic disease which is killing birds across Britain.
Thousands of Britain's most colourful garden bird species are falling victim to the infection, trichomoniasis, which is spread by contact, especially at bird tables and bird feeders.
Householders with feeding equipment are being asked to disinfect it regularly in an attempt to control the disease, whose severity may have been accentuated by the warm wet summer - a hot July followed by a damp August.
Greenfinches, chaffinches, goldfinches and house sparrows are among the species being struck down by an ailment which in the past has been confined to doves and pigeons (woodpigeons and collared doves in particular), and the birds of prey that feed on them, such as sparrowhawks, as well as domestic fowl.
It is not harmful to humans or domestic pets such as cats and dogs.
The disease is caused by the trichomonas parasite which causes infections to develop at the back of the throat and gut.
Affected birds tend to be lethargic and have fluffed-up plumage, and may drool saliva, experience difficulty in swallowing and show laboured breathing. The disease may progress over several weeks, so some birds become very emaciated before they die.
Since midsummer the British Trust for Ornithology (BTO) has been receiving reports of the outbreak from across the country: the first came from Wales, the Welsh borders and the West Country, but now the disease has spread to all regions. Finch species appear to be particularly vulnerable, with one report of 600 greenfinches found dead at Builth Wells, Powys.
A total of 25 species, from robins and starlings to siskins and yellowhammers, have been affected so far this year, according to the Royal Society for the Protection of Birds, which has reports from 40 counties across England, Wales and Scotland.
Feeding points where birds congregrate are thought to be one of the prime sources of infection. More and more people have erected bird tables or placed feeders in their gardens in recent years, with some estimates putting the current worth of the birdfood market at nearly £200m a year.
"It is certainly starting to look serious," said Paul Stancliffe of the BTO. "We are now encouraging people to take preventative measures. You should continue to feed the birds in your garden, because if they don't use yours, they will just use somebody else's. But you should properly clean your feeding equipment and wash down your bird table. There are proprietary products available, or you can do it with a weak solution of domestic disinfectant. You should also change the birds' water regularly."
The parasite was generally spread by beak-to-beak contact, Mr Stancliffe said, but, unusually, there was evidence that it could live for up to five days outside its host, so grain or water at the feeding stations might become infected and carriers of the disease.
It was hoped that with the onset of cold weather the disease would start to tail off, he said.
An RSPB spokesman, Andre Farrar, also stressed the importance of cleaning bird tables and feeders. "We wouldn't want the act of bringing birds together to be the cause of disease amongst them," he said. Mr Farrar said the RSPB was monitoring the situation, but it had not yet reached "conservation levels" of concern.