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Celebrating the power of Citizen Science

News Item 2020

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The latest Breeding Bird Survey (BBS) report – The Breeding Bird Survey 2019 – covering population trends for the UK’s bird species has been released today. This report is a celebration of the dedication of the volunteers who give up their time and take part in bird surveying; collectively they walked 14,996 km whilst actively surveying in 2019.

The distance walked in 2019 is the equivalent of walking from the BTO’s headquarters in Norfolk to Palmer Land in Antarctica! Since the survey began in 1994, the total distance walked by BBS volunteers is a staggering 299,701 km, almost seven and a half times around the world! But what has it told us?

The report, covering the population changes of the UK’s breeding birds, shows that one of our most widespread and common birds is in trouble and disappearing from large parts of the country, and how skilled volunteers are helping to monitor the changes as they unfold.

The Greenfinch is a familiar bird, being a frequent visitor to garden feeding stations across the UK, but how much longer might this be the case? The 2019 Breeding Bird Survey results show an alarming decline. During the last 23 years, the Greenfinch population has fallen by 64%.

The main driver behind this change is a parasite that causes a disease called trichomonosis. Known as a disease in cage birds for some time, it was first noted in British finches in 2006. Infected birds become lethargic, have fluffed-up feathers and are unable to swallow food. Transmission between birds can be via contaminated food and water (e.g. at garden feeding stations). Good feeding station hygiene, with regular cleaning and disinfecting can help to slow the spread. The Trichomonas gallinae parasite is a parasite of birds and does not pose a health risk to humans or their mammalian pets.

In contrast, the UK’s commonest bird, the Wren, just got even more common, with an increase of 30% over the last 23 years as reported by the Breeding Bird Survey. This translates to around 11,000,000 Wrens across the UK, as calculated using BBS trend changes and historic estimates and published in another bird monitoring report, APEP. A run of mild winters no doubt contributing to the 30% increase since 1994 as revealed by the BBS Report.

It is now possible to monitor the population changes for 117 bird species and it is all thanks to the dedication of the thousands of BBS volunteers who go out every spring to survey the UK's bird life.

Sarah Harris, BBS Organiser, said "I am always amazed by the power of citizen science, the dedication of volunteers and in turn, the difference their observations can make to conservation and research. The Greenfinch is still found across the UK and you might be forgiven for thinking nothing is amiss, but as the BBS shows, nothing could be further from the truth – thanks to all those who take part we are able to keep an eye out for changes in bird populations.”

Paul Woodcock, Biodiversity Evidence Specialist at JNCC, said, "The report really highlights the huge contribution made by BBS volunteers up and down the country, and shows that the high-quality data can help understand when, how and why bird populations are changing. Thank you to everyone involved"

Mark Eaton, RSPB’s Principal Conservation Scientist, said "Greenfinches are fantastic little birds, and the flashes of green and yellow used to be a common sight at our bird feeders. The food we put out for these little seed-eaters has become increasingly important over the years, as food availability in the wider countryside has reduced. Continuing to provide food is important but you can help them, and other birds, by cleaning your feeders and water sources every couple of weeks with a mild disinfectant."

The BTO/JNCC/RSPB Breeding Bird Survey is a partnership jointly funded by the BTO, RSPB and JNCC, and the report is published by BTO annually on behalf of the partnership.

The The Breeding Bird Survey 2019 provides trends for all 117 species covered by the Breeding Bird Survey.


Contact Details:

Paul Stancliffe
(BTO Media Manager)
Mobile: 07585440910


Population trends for 117 bird species in the UK have been calculated in the latest BTO/JNCC/RSPB Breeding Bird Survey (BBS) annual report. BBS is the main scheme for monitoring the population changes of the UK’s common breeding birds.

In 2019, 4,005 BBS squares were covered in the UK by volunteers. The latest report can be found at

The Breeding Bird Survey (BBS) Partnership: The BTO/JNCC/RSPB Breeding Bird Survey is a partnership jointly funded by the BTO, RSPB and JNCC, with fieldwork conducted by volunteers.

Details of other official statistics produced by JNCC and its partners can be found on our Official Statistics webpage.

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