Birds benefit from a Christmas break

01 Nov 2010 | No. 2010-10-40

The latest figures from British Trust for Ornithology (BTO) bird ringers show that the harsh winter took its toll on the resident birds that stayed behind to weather it, but the migrants returned from their winter break to produce a bumper crop of nestlings.

  20% fewer Wrens were caught by volunteer
bird ringers during CES

When the days become greyer and the nights draw in, so the idea of heading off to warmer climes to sit out the winter becomes more and more appealing. Despite the numerous hazards facing them on their long journey south, a whole host of migrant birds do just that. And as average temperatures fell to a 30-year low over the winter of 2009/10, many of our Robins and Wrens began to regret not joining the departing flocks themselves.

The latest figures produced by the BTO’s Constant Effort Site (CES) project showed that volunteer bird ringers at 70 sites across the country caught 27% fewer Robins and 20% fewer Wrens compared to average catches over the previous five years, while Dunnock and Greenfinch numbers also fell significantly. A Christmas break was obviously the sensible option, as our summer visitors returned to a better summer than has been the norm in recent years and prospered in the mild weather.

The cold, wet summers of recent years do make you wonder why some of our migrant birds even bother coming back” said Greg Conway, organiser of the CES scheme. “The 2010 breeding season was a complete contrast, however, with good numbers of birds returning and producing bumper broods – a great result for them and for the ringers!”

The numbers of returning Blackcap, Whitethroat and Reed Warbler were higher than average and many migrant species produced significantly more nestlings than in recent years, including the amber-listed -Willow Warbler, which experienced a 42% increase in breeding success. “Blue Tit, Great Tit and Chaffinch also appeared to have had a productive nesting season” explained Greg, “Blackbirds didn’t do so well though, possibly because the early summer weather was too good, making it harder to find worms and insects for their chicks as the soil became drier and more compacted

To see the full report please visit

CES Results

CES Results (PDF, 337.95 KB)

Notes for Editors

The results are analysed from information collected by the BTO/JNCC Constant Effort Site ringing scheme. The Constant Effort Sites (CES) scheme is the first national standardised ringing programme within the BTO Ringing Scheme and has been running since 1983. Ringers operate the same nets in the same locations over the same time period at regular intervals through the breeding season at 120 sites throughout Britain and Ireland. The Scheme provides valuable trend information on abundance of adults and juveniles, productivity and also adult survival rates for 25 species of common songbird.

The Constant Effort Sites scheme is funded by a partnership of the BTO, the JNCC (on behalf of Natural England, Scottish Natural Heritage, the Countryside Council for Wales, and also on the behalf of the Environment and Heritage Service in Northern Ireland), Duchas the Heritage Service - National Parks and Wildlife (Ireland) and the ringers themselves.

The BTO is the UK’s leading bird research organisation. Over thirty thousand birdwatchers contribute to the BTO’s surveys. They collect information that forms the basis of conservation action in the UK. The BTO maintains a staff of 100 at its offices in Norfolk and Stirling, who analyse and publicise the results of project work. The BTO’s investigations are funded by government, industry and conservation organisations.

The Joint Nature Conservation Committee (JNCC) is the statutory adviser to the UK Government and devolved administrations on UK and international nature conservation. Its work contributes to maintaining and enriching biological diversity, conserving geological features and sustaining natural systems.

Contact information 

Paul Stancliffe (BTO Press Officer)
Office: 01842 750050 (9am to 5.30pm)
Mobile: 07845 900559 (anytime)
Email: press [at]

Greg Conway (CES Organiser)
Office: 01842 750050 (9am to 5.30pm)
Mobile: 07845 900559
Email: press [at]

Images are available for use alongside this News Release
Please contact images [at] quoting reference 2010-10-40

The BTO has an ISDN line available for radio interviews
Please contact us to book an interview
Office: 01842 750050

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