Chiffchaff © Amy Lewis
The 20th annual BirdTrends report from the British Trust for Ornithology (BTO), just published, gives the latest information on the winners and losers in the British countryside.The report highlights the rapid and continuing decline of the Greenfinch, which has declined by 59% in the UK in just ten years, and raised a high level alert against longer-term trends for the first time.
The Greenfinch is a familiar garden bird which was not a conservation concern when the UK’s list was last updated (in 2015), but could be moved straight to the ‘red list’ (which indicates the species of greatest concern) when the list is next updated, should the decline continue at its current rate. The decline is caused by a widespread and severe outbreak of a disease called trichomonosis, which first affected bird populations in 2006.
One species that is doing particularly well is the Chiffchaff, which is continuing to increase its breeding range and population. Record numbers of this small green warbler were caught by bird ringers on their constant effort ringing sites. This species is benefitting from warmer winters. Once a very rare sight in winter, it can increasingly be seen on sunny days in sheltered locations throughout the UK, particularly in the milder coastal areas and around inland waterbodies.
The BirdTrends report covers 120 of Britain’s commonest and most widespread birds, from Mute Swan to Corn Bunting, and it makes for interesting reading. The data covered in the report were gathered by thousands of volunteer ‘citizen scientists’ who each year record the birds on their patch to track how well they are doing.
Some count the birds they record on two early morning survey visits. The Breeding Bird Survey covers all habitats and volunteers are allocated a nearby square from a pre-selected list. Volunteer Alan Gomersall was initially disappointed not to get a square in the countryside but, after twenty years of recording in a Bedfordshire housing estate, says “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; in 2003 I counted 50 Greenfinches, this year they were down to just five.”
Others contribute data from their bird ringing sessions, which they run in a comparable way each year. Andy Coates operates Scotland’s second-longest running constant effort site near Edinburgh Airport. Andy says “working with a great team of people makes the early morning sessions enjoyable and we’ve really noticed the increase in Chiffchaffs in the last few years”.
Dr Dario Massimino, lead author of the report, said, "Each year I am able to bring together information from six of the BTO's core surveys in order to produce the thousands of graphs and tables which the BirdTrends pages are composed of. It is exciting to be one of the first people to get the full picture of the trends of the 120 species included in the report."
Dr Rob Robinson, one of the authors of the report at the BTO, said ”This report presents the results of many thousands of hours by volunteers looking out for birds in every habitat – from the streets of Cambridge to the slopes of the Cairngorms. It is only thanks to their effort we know so much about the health of our bird populations.”
The report is produced in partnership by the BTO and the Joint Nature Conservation Committee (JNCC).
To access the report, please visit https://www.bto.org/about-birds/birdtrends/2017
