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Published Date: 2017-12-26 11:10:52
Subject: PRO/AH/EDR> Trichomoniasis, avian - UK: (England) bird population declines
Archive Number: 20171226.5523091
A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases

Date: Thu 21 Dec 2017
Source: Daily Mail [edited]

A much-loved bird is disappearing from UK gardens because of a deadly disease, with numbers more than halving in a decade, new research has warned.

The greenfinch's colourful plumage and distinctive twittering once made it one of our most familiar feathered friends. But numbers have plunged by an alarming 59 per cent in just 10 years, sparking concerns for its very future on these shores, warn bird watchers.

The decline is caused by a widespread and severe outbreak of a disease called trichomoniasis, 1st seen in finches in the UK in 2005.

The disease -- also known as canker or bird bath disease -- is spread by waterborne parasites on bird tables and also affects pigeons.

The scale of the greenfinch's rapid decline has shocked experts and raised a high level of alert for its long-term health for the 1st time. It was not even a conservation fear when the UK's list of endangered birds was last updated in 2015. But now it faces being moved straight to the "red list," indicating species of greatest concern, should the decline continue at the current rate.

The British Trust for Ornithology's (BTO's) BirdTrends report covers 120 of the commonest and most widespread birds, ranging from Mute Swan to Corn Bunting. Report lead author Dr Dario Massimino said: "Greenfinch abundance fluctuated somewhat up to the mid-1990s, but there was little change in either survival or breeding performance during this period. More recent CBC/BBS (Common Birds Census/Breeding Birds Survey) data indicate population increases widely across the UK, followed by a sudden sharp fall induced by a widespread and severe outbreak of trichomoniasis, which affects the upper digestive tract, that began in 2005."

The report added that the current decline could cause it to be rated "Endangered" under IUCN (International Union for Conservation of Nature) guidelines, although it is currently on the green list of low concern.

A BBS map between 1994-96 and 2007-09 indicates that increases over that period in East Anglia and western Britain were offset by decreases in eastern Northern Ireland, northeastern Scotland, and central southern England.

Dr Massimino said: "The subsequent, disease related decrease is ongoing in all parts of the UK. Productivity data are complex, with a slight increase in nest survival at the egg stage but minor decreases in clutch and brood sizes and the number of fledglings per breeding attempt. The trend towards earlier laying may be explained by recent climate change. Numbers across Europe have been broadly stable since 1980."

The figures were gathered by thousands of citizen scientists who each year record the birds on their patch to track how well they are doing.

Volunteer Alan Gomersall said: "In 2003, I counted 50 greenfinches; this year [2017], they were down to just 5."

Some count the birds they record on 2 early morning survey visits. The Breeding Bird Survey covers all habitats, and volunteers are allocated a nearby square from a pre-selected list.

Mr Gomersall was initially disappointed not to get a square in the countryside. But, after 20 years of recording in a Bedfordshire housing estate, he said: "I am glad I continued. I have found a surprising number of different species over the years, and it has been fascinating to see the changes."

Trichomoniasis makes the birds' throats swell, meaning they starve to death. It is spread by dirty bird tables. Householders are urged to clean them.

The parasite that causes the disease, _Trichomonas gallinae_, has long been known in pigeons and doves and somehow spread from these birds into finch populations. While greenfinches have been most badly hit, the disease has also been diagnosed in a number of other bird species, including the house sparrow and yellowhammer, both of which are already red listed, according to the report. But one species that is doing particularly well is the chiffchaff, which is continuing to increase its breeding range and population.

The report said record numbers of this small green warbler have been caught by bird ringers, thanks to warmer winters. Once a very rare sight in winter, it can increasingly be seen on sunny days in sheltered locations throughout the UK, especially in the milder coastal areas and around inland waterbodies.

Others contribute data from their bird ringing sessions, which they run in a comparable way each year.

[Byline: Colin Fernandez]

Communicated by:
ProMED-mail from HealthMap Alerts

[_Trichomonas gallinae_ is a common protozoan parasite of pigeons (_Columbiformes_), which principally infects the upper alimentary tract where it can cause necrotic ingluvitis. Epidemic mortality in columbiform species has been previously reported, and the parasite infrequently infects other avian taxa such as birds of prey and songbirds.

In the USA, trichomoniasis has been postulated to be a factor contributing to the extinction of the passenger pigeon _Ectopistes migratorius_ and has been shown to be a significant cause of nestling mortality in the island-endemic pink pigeon _Nesoenas mayeri_ and in the Iberian Peninsula population of the Bonelli's eagle _Hieraaetus fasciatus_.

The European green finch (_Chloris chloris_) is a small passerine bird spread throughout Europe. For a picture of a male (above) and a female (below) go to

Portions of this comment were extracted from - Mod.PMB

HealthMap/ProMED-mail map:
England, United Kingdom:]

See Also

Trichomoniasis, avian - UK: (England) garden birds 20130912.1939358
Trichomoniasis, avian - Ireland: garden birds 20130207.1533305
Trichomoniasis, avian - Germany: (BY) finch, susp 20120704.1190095
Trichomoniasis, avian - Europe: finch 20110925.2915
Trichomoniasis, avian - UK: finch 20100825.2990

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