BBS is the main monitoring scheme for recording common breeding birds in the UK. The data are used to create UK-wide population trends for 119 bird species, and country or regional trends for those species where there are adequate data.
Volunteers can also optionally monitor mammals in their sites. These additional data are used to create population trends for nine mammal species.
As of 2009, BBS has linked up with the UK Butterfly Monitoring Scheme (UKBMS). Volunteers are encouraged to visit their sites again later in the year to carry out the Wider Countryside Butterfly Survey (WCBS) to collect co-located bird and butterfly data for enhanced data use.
Background
BBS is a partnership between JNCC, the British Trust for Ornithology (BTO) and the Royal Society for the Protection of Birds (RSPB).
The BBS was launched in 1994 when it replaced the Common Birds Census (CBC). The two programmes ran parallel for seven years to facilitate comparison of the two datasets and creation of long-term, combined trends that for some species go as far back as the 1960s.
BBS would not be possible without the dedication and support of thousands of talented volunteers. Since the scheme began, approximately 9,000 volunteers have collected nearly eight million records of around 300 species of bird. Using the Heritage Lottery Foundation figures, the time volunteers dedicated to BBS in the 2021/2022 season was valued at around £627,340.
Why do we monitor breeding birds?
Many groups of UK birds, such as insectivores and farmland birds are experiencing long term declines and therefore may need conservation intervention to protect them. To make appropriate conservation decisions, it is important that we are well informed of the breeding status of these birds. BBS allows us to see which species are increasing (potentially where conservation has worked, such as the Skylark) and decreasing (where more effective conservation is needed, such as the Turtle Dove) or where other unexpected pressures start impacting on a species (such as the decline in Greenfinch caused by trichomonosis).
Birds are also comparatively easy to monitor and are charismatic, making them a good group to raise engagement and awareness of conservation issues in the wider public.
BBS results are published annually as Official Statistics and are used widely to assess the effectiveness of conservation actions, to measure country and UK progress towards national and international goals (including UK Biodiversity Indicators C4a and C5), and to help inform new conservation measures.
The large BBS sample size makes it a valuable resource for exploring the reasons for change both in policy and academic research. The dataset can be used alongside other data sources to investigate the causes of declines and birds’ responses to changing climates and anthropogenic activities. See some of these papers on the BBS webpages. This information is vital to be able to make informed and effective management and conservation decisions, and to understand birds’ responses to environmental and anthropogenic changes.
BBS data are also routinely shared with the Pan-European Common Bird Monitoring Scheme (PECBMS) which collates bird monitoring data from across Europe. Many of the uses of PECBMS data mirror those at the UK level, e.g. in informing and assessing policy, but for the European Union.
Sampling approach/how are the data collected?
BBS consists of the main BBS surveys, where volunteers are randomly allocated a 1 X 1 km square or for the Waterways Breeding Bird Surveys (WBBS) volunteers are allocated a single line transect along a 500-5,000 m stretch of river or canal. Both BBS and WBBS surveys follow the same distance sampling-based method and record all birds seen or heard, but WBBS surveys are particularly important to capture data on specialists of linear waterways.
In each square, two 1 km transects are mapped out and further divided into five 200 m sections for surveying.
The aim is that volunteers will survey the same site(s) every year, maintaining a consistent approach by surveying at approximately the same time of year and time of day each year. Only sites that have been surveyed for at least two years are added to analyses of population trends.
Each transect is surveyed twice in spring/early summer. The first visit is conducted between April and mid-May, the second between mid-May and June.
Volunteers are encouraged to walk their transects in the early morning when birds are most active but after the highly concentrated dawn chorus, on days when the weather will not discourage bird activity (such as through strong winds or heavy rain).
When walking a transect, volunteers should record every bird they see or hear, and the distance band that the bird was seen/heard in. Volunteers are also able to optionally record mammals. Notes of the weather conditions using a three-level weather code system to describe cloud cover, rain, wind and visibility at the time of the survey are also recorded.
In 2014, habitat recording was made a mandatory feature of the survey, volunteers recording the habitats within 25 m of the transect lines according to the Crick habitat classification.
How and where data/results are available to stakeholders
The BTO BBS latest results page houses the annual BBS report, UK national and region trends, and country, region and county summaries. BBS data can also be requested through BTO’s online data request system.
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