The Constant Effort Sites Scheme (CES)

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 over 130 sites throughout Britain and Ireland.

The Scheme provides valuable trend information on abundance of adults and juveniles, productivity and also adult survival rates for 24 species of common songbird.

The Partners

The Constant Effort Sites Scheme is supported by a partnership between the British Trust for Ornithology (BTO) and the Joint Nature Conservation Committee (JNCC) (on behalf of: The Department of the Environment Northern Ireland, Natural England, Natural Resources Wales and Scottish Natural Heritage). It is also part of the BTO Ringing Scheme which is funded by the BTO/JNCC Partnership, The National Parks and Wildlife Service (Ireland) and the ringers themselves.


Latest CES News


2015 NRS & CES preliminary breeding season results

Chaffinch. Photograph by Jill Pakenham

Chaffinch abundance and productivity declined significantly in 2015.

Information collected by BTO volunteers shows that numbers of many resident bird species, and some migrants, increased in 2015. However, the spells of cool, wet weather that much of Britain & Ireland experienced in late-spring and summer left many birds struggling to breed, with more northerly populations faring particularly badly. See the preliminary breeding season report for details.





Life Cycle cover image

Life Cycle is available to read online or download as a PDF

Introducing Life Cycle

The first edition of Life Cycle, the BTO magazine for Ringers and Nest Recorders, is now available to download as a  PDF (PDF, 3.74 MB)  or to read online. The bi-annual magazine replaces the old scheme newsletters, back issues of which are still available via the following links - Ringing News (available on the ringers-only pages of the website), NRS NewsCES News and RAS NewsLife Cycle includes practical ringing and nest finding tips, details of novel techniques and summaries of successful monitoring projects that demonstrate the initiative, hard work and skill of existing volunteers, while hopefully inspiring others to set up their own studies. We hope you enjoy reading it!



Willow Warbler. Photograph by Jeff Kew

2014 was the worst year for Willow Warbler abundance since CES began

2014 CES and NRS results

The warm, settled weather that graced Britain & Ireland in the spring and summer of 2014 resulted in a bumper bird breeding season. Information collected by BTO volunteers shows that although not all of our summer migrants returned to take advantage of the conditions, those that did were generally successful in rearing the next generation. 

See the NRS and CES Preliminary Report for details.





Weather Guidance for CES ringers is published on the Taking Part page.