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BirdTrends 2011: trends in numbers and demography for UK breeding birds
A population trend for Barn Owl is newly available from BBS: it indicates a clear
increase in this species since 1995, though there is some extra uncertainty around
trends for nocturnal species


Key findings

Species list


Using the BirdTrends pages

These pages are a one-stop shop for information about the population status of the common birds of the wider UK countryside. It is based on data gathered by the many thousands of volunteers who contribute to BTO-led surveys. With one web page per species, users can quickly find all the key information about trends in population size and breeding performance over the period 1966–2010, as measured by BTO monitoring schemes. 

The summary of key findings provides a brief overview of our main findings this year. For each species, we provide:

  • General information concerning species' conservation listings and UK population sizes
  • A brief summary of observed changes in the size of the population and information concerning the possible causes of these changes
  • A series of graphs and tables showing the trends and changes in population size and breeding performance over the past 42 years
  • Trends calculated from BTO/JNCC/RSPB Breeding Bird Survey (BBS) data, not only for the UK as a whole but also for each of its constituent countries (England, Scotland, Wales and Northern Ireland)
  • Alerts that highlight population declines in any census scheme of greater than 25% or greater than 50% that have occurred over the past 5 years, 10 years, 25 years and the maximum period available (usually 42 years).

Increasingly, further information on demography and causes of change is being added.

Other pages provide details of the field and analytical methods that were used to produce the results for each species and of the methods used to identify alerts. We discuss overall patterns of trends in abundance and breeding success, and compare the latest trend information and alerts with the Birds of Conservation Concern list (Eaton et al. 2009). Four summary tables list alerts and population changes by scheme, and there is also a facility to select and display your own tables of population change. A detailed references section lists more than 300 of the most relevant recent publications, with onward links to abstracts or full text where freely available, and is a valuable key to recent scientific work by BTO and other researchers; some species pages also contain a reference list. Results and conclusions are summarised under Key findings.

The website covers the majority of UK breeding birds, 117 species in total, but excludes (with a few exceptions) colonial seabirds, which are well covered by the JNCC's Seabird Monitoring Programme, and the rare species that are included in the reports of the Rare Breeding Birds Panel (e.g. Holling & RBBP 2007b, 2008, 2009, 2010a, 2010b, 2011). 

We value your comments on this report and particularly any suggestions on how it can be improved.

john.marchant [at] bto.org (Email your comments)


These web pages constitute an annual report that is part of the BTO research report series. Authors were Stephen Baillie, John Marchant, David Leech, Anna Renwick, Sarah Eglington, Andrew Joys, David Noble, Carl Barimore, Greg Conway, Iain Downie, Kate Risely and Rob Robinson. The formal citation for the report is given in the page footer.


This report should be cited as: Baillie, S.R., Marchant, J.H., Leech, D.I., Renwick, A.R., Eglington, S.M., Joys, A.C., Noble, D.G., Barimore, C., Conway, G.J., Downie, I.S., Risely, K. & Robinson, R.A. (2012) BirdTrends 2011. BTO Research Report No. 609. BTO, Thetford. http://www.bto.org/birdtrends