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Parasite hits greenfinches

PUBLISHED: 10:53 20 August 2010 | UPDATED: 11:57 16 September 2010

The number of greenfinches across Norfolk has fallen by more than a third following the emergence of a new disease, according to experts.

Trichomonosis, an infectious disease of garden birds, has led to a dramatic decline in greenfinch populations across central England, with numbers down by 36pc.

The number of greenfinches across Norfolk has fallen by more than a third following the emergence of a new disease, according to experts.

Trichomonosis, an infectious disease of garden birds, has led to a dramatic decline in greenfinch populations across central England, with numbers down by 36pc.

The figures, produced by the Garden Bird Health initiative and the Thetford-based British Trust for Ornithology (BTO), cover the period from 2005 to 2007.

Graham Appleton of the BTO said trichomonosis was not very apparent in Norfolk until 2007, but had taken its toll since, estimating that the number of greenfinches had fallen by a similar number across the county.

The findings also reveal that chaffinch populations fell by up to 20pc. Most birds died in the summer and autumn months, and outbreaks of the disease continued to occur each year since emerging in 2005.

Trichomonas gallinae, the cause of the disease, is a protozoan parasite and a well-known cause of disease in pigeons and doves, and birds of prey that feed on them.

In 2005, trichomonosis was first recognised as a cause of disease in finches. The chaffinch has also been hit by the parasite which cannot survive for long outside the host.

Mr Appleton said: “This is a parasite that has been in pigeons for years, but seems to have jumped to other species in 2005. Greenfinches seem particularly at risk, possibly because they spend so much of their time feeding together.”

Greenfinches, which weigh about an ounce, are the ninth most common garden bird in Norfolk.

Mr Appleton said: “This is really interesting research because it's not often you pick up the emergence of a disease in a species. It's not going to cause the extermination of all greenfinches; it was in pigeons and doves, and there are still a lot of them around. It will take out a large part of the population, but they will learn to resist and cope with it.”

He added that people could help combat the spread of trichomonosis by feeding birds and ensuring bird table are kept as clean as possible, with water in bird baths changed regularly.

“Greenfinches are very messy eaters and spit out a lot of the food they eat. Another bird will pick it up and that's how the parasite spreads.

“Birds benefit hugely from the seeds that we supply in our gardens, especially when it is tough to find food elsewhere.

“People who are concerned about this disease need to make sure that their feeding stations are the cleanest restaurants in town.”

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