Bird Surveyors help to shed new light on changing mammal populations

08 Aug 2018 | No. 2018-22

The UK’s mammals present particular challenges for monitoring; they live in a wide variety of habitats, vary enormously in size and can be very difficult to see, but Britain’s army of volunteer bird surveyors could come to the rescue.

In a scientific paper, just published in the journal Biological Conservation, British Trust for Ornithology (BTO) scientists reveal how and where numbers of nine UK mammal species are changing, using data collected by the BTO/JNCC/RSPB Breeding Bird Survey (BBS), and it makes for interesting reading. Three of the four deer species monitored show increasing abundance across a significant part of their UK ranges, with only Red Deer appearing stable. One of the biggest surprises, however, is the large scale declines in Red Fox populations in the countryside; in central-southern England and Wales between 20% and 50% of foxes have been lost in the last 20 years.

There is no single survey technique that adequately covers all of Britain’s mammals but some mammals are known to cause problems for other species or to cause economic damage, while others are of conservation concern; having a robust assessment of their populations is a priority.

One way to achieve this is to tap into an existing monitoring framework, aimed at different taxa but through which additional data can be collected. This is already done by the volunteers participating in the BBS. This survey, which was launched in 1994 to monitor widespread breeding birds, has since been extended to include mammals. Robust mammal trends are now produced annually, for the UK, for the four individual countries and for nine English regions using data collected by BBS volunteers.

Dario Massimino, lead author on the paper, said, “The results of this work demonstrate how, given a structured approach and an established network of keen volunteers, it is possible to produce valuable information on other species. Of course, there are strengths and limitations to adding a different group of species to an existing survey, but, as this paper demonstrates, the ability to monitor the changing status of nine mammal species provides much-needed information.”

The full paper can be accessed here 

Contact Details

Paul Stancliffe
(BTO Media Manager)
Office: 01842 750050
(9am to 5:30pm Mon-Thurs), (9am to 5pm Friday)
Mobile: 07585 440910
Email: press [at] ()

Dario Massimino
(Research Ecologist)
Office: 01842 750050
(9am to 5:30pm Tues -Thurs), (9am to 5pm Friday)
Email: dario.massimino [at]

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Notes to editors

1. The British Trust for Ornithology (BTO)/Joint Nature Conservation Committee (JNCC)/Royal Society for the Protection of Birds (RSPB) Breeding Bird Survey (BBS
) is a partnership jointly funded by the BTO, JNCC and RSPB, with fieldwork conducted by volunteers. This partnership also funded the work presented in this paper.

2. Biological Conservation is an international leading journal in the discipline of conservation biology. The journal publishes articles spanning a diverse range of fields that contribute to the biological, sociological, and economic dimensions of conservation and natural resource management. The primary aim of Biological Conservation is the publication of high-quality papers that advance the science and practice of conservation, or which demonstrate the application of conservation principles for natural resource management and policy. Therefore it will be of interest to a broad international readership.

3.The BTO is the UK's leading bird research charity. A growing membership and up to 60,000 volunteer birdwatchers contribute to the BTO's surveys, collecting information that underpins conservation action in the UK. The BTO maintains a staff of 100 at its offices in Thetford, Stirling, Bangor (Wales) and Bangor (Northern Ireland), who analyse and publicise the results of surveys and projects. The BTO's work is funded by BTO supporters, government, trusts, industry and conservation organisations.

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