Trichomonosis insight

The impact that diseases have on bird populations is a fascinating topic of research, to which ringers and members of the public can contribute. Many will now be aware of the detrimental effect that Trichomonosis has had on Greenfinch populations in the UK, a relationship established by a piece of research led by scientists at the Institute of Zoology in London and the BTO. A subsequent study from the same team also showed, through molecular analyses, that the disease arrived in Fennoscandia from the UK in 2008, most likely carried by Chaffinches. This link was identified thanks to the known migration route of this species provided by previous ringing data.

Greenfinch showing signs of Trichomonosis by Heather Povey

A project by different authors has recently showed that Trichomonosis spread in Finland in 2008 and 2009 and impacted local Greenfinch and Chaffinch breeding populations. In August-September 2008 the first cases of this disease had appeared in the country, followed by a peak in reported mortality in July 2009, although cases diminished in 2010 to pick up again in 2011. The Finnish study showed that population of breeding Greenfinch declined by 47% in south Finland, but not other parts of the country, at the peak of the outbreak between 2009 and 2010, whilst Chaffinch declined by 4%, between 2006 and 2010, the first population decrease since 1984. Bird body condition was also affected by the disease. Ringing data highlighted that Greenfinches, especially juveniles, were lighter than usual over the autumns 2008 and 2009 in the areas most affected by Trichomonosis.

These studies are a very good example of the important contribution to science that members of the public and ringers provide by reporting changes in birds and garden wildlife, as well as the unique high-quality data and essential information that ringing provides.

For more background information, visit the BTO GBW webpage

Daria Dadam, Research Ecologist