Blog by Andrew Stanbury, Conservation Scientist, RSPB Centre for Conservation Science

The International Union for Conservation of Nature (IUCN) is a global authority on the state of the natural world, and the process used to create their Red List of Threatened Species is widely recognized as the most comprehensive, objective approach for evaluating the conservation status of plants and animals across the globe. Working with colleagues at the RSPB Centre for Conservation Science, in close collaboration with scientists at Natural England (NE), British Trust for Ornithology (BTO), Game & Wildlife Conservation Trust (GWCT), Joint Nature Conservation Committee (JNCC) and Wildfowl & Wetlands Trust (WWT), I have just published an analysis that shows that nearly 40% of British bird populations are formally classed as ‘Threatened’ with extinction when assessed using the standard IUCN Red-List Categories and Criteria.

The RSPB, and other conservation organisations, use regular ‘Birds of Conservation Concern’ (BoCC) assessments to help identify their priorities for bird conservation in the UK. This in-depth process allocates each UK species to one of three lists (Red, Amber and Green) depending on their conservation concern. The most recent, BoCC4, was published in 2015.

Undertaking such status assessments requires detailed up-to-date information on species’ population sizes, trends and ranges, amongst other things. Fortunately, here in the UK we are able to call upon the efforts of a large number of dedicated volunteers who take part in long-term monitoring schemes such as the BTO/JNCC/RSPB Breeding Bird Survey (BBS) and BTO/RSPB/JNCC Wetland Bird Survey (WeBS). These, and other schemes, provide the robust data required for assess species against the BoCC criteria.

However, the data needed to carry out a BoCC-type assessment are not often available for other taxonomic groups in Britain or elsewhere in the world and the IUCN Red List process has come to be widely used. This categorises species according to their likelihood of extinction, using existing information (not necessarily of high quality) to classify them as either Extinct, Regionally Extinct, Critically Endangered, Endangered, Vulnerable, Near Threatened or Least Concern, depending on factors such as population/range size and decline.

Photo: The British kittiwake population has declined by an estimated 54% over the last three generations (39 years); however, if the current trend continues, and there is no evidence to suggest it won’t, the species is predicted to exceed the Critically Endangered threshold in the next ten years, RSPB Images

The IUCN Regional Red List differs from the approach used in BoCC in a number of ways, but most crucially in its overall aim. The IUCN process is solely concerned with whether a species might go extinct at the geographical scale being considered, whereas BoCC assessments consider a rounded suite of reasons why we might have concern for a species, for example, its historical status and the international significance of our population. As a result, the IUCN approach tends to highlight species that are either declining currently or have small population sizes/ranges, but not (for example) those which may have declined in the more distant past, but have been stable more recently. 

The main benefit of the IUCN approach is that it uses globally standardised criteria, and so the results of assessments are in theory comparable across different taxonomic groups, or between assessments for the same taxa made in different regions. This is exactly why we have undertaken the assessment – to enable the threat of extinction faced by birds to be assessed alongside those of other species – both here and abroad.

Our study represents the first formal assessment of extinction risk of British birds using the standard IUCN Regional Red-List process. We found that 43% of the 234 regularly occurring species assessed had at least one population (breeding or non-breeding) that qualified as Threatened with extinction in Britain. At an individual population level (we assessed wintering populations separately where the population at least doubled outside the breeding season) 39% were assessed as Threatened, with 8% classed as Critically Endangered, 14% Endangered and 17% Vulnerable. An additional 10% of populations were classified as Near Threatened. Golden oriole and fieldfare, both Critically Endangered, are on the verge of being lost as breeding species in Britain; potentially joining seven other species that are already classed as being extinct as breeding species. Other Critically Endangered species, including turtle dove, redwing and marsh warbler, and non-breeding populations of Bewick’s swan and smew, are at risk of going the same way.

There are many similarities between the outputs of BoCC and our new IUCN Regional Red List, but the use of different assessment criteria is bound to result in differences.  The IUCN process does not highlight some of the species red-listed by BoCC, such as skylark and house sparrow, whose populations are considered depleted. Although we consider it important to help populations of these species to recover, their populations and trends in numbers remain well above levels that might lead us to consider them at imminent risk of extinction. Conversely, three species that were Green-listed by BoCC4, chough, woodlark and greenfinch, are considered at risk of extinction from Britain by the IUCN process; the latter species has undergone large declines over the last decade. 

Photo: Greenfinch qualified as being Endangered in Britain. Though the species increased in numbers during the first 10 years of the Breeding Bird Survey, it has declined consistently since 2005 because of a widespread and severe outbreak of the protozoan parasite trichomonosis, RSPB images

Whilst the scale of threat facing our birds is considerable, there is much we can do – and indeed much we are doing - not only to halt extinction but to help reverse decline and restore healthy ecosystems and landscapes. Our targeted recovery programmes, for example, have effected modest recoveries in species such as stone-curlew, corncrake and cirl bunting whilst others, included our work to recover bitterns and bring back the red kite, have been resounding successes.

‘Birds of Conservation Concern’ will continue to be the principal reference for identifying bird conservation priorities in the UK; however, the new Regional IUCN Red List assessment provides an additional way of interpreting the status of our birds. It allows for like for like comparisons of the status of birds in Britain with other taxonomic groups in this country, and elsewhere in the world. Furthermore, the fact that 23 species have been formally assessed as being Critically Endangered with extinction from Britain sends out a powerful conservation message.

 The assessment represents Number 34 in the GB Species Status series and was funded by RSPB and Natural England as part of the ‘Action for Birds in England’ partnership. A paper describing the assessment and its results is in the September issue of the journal British Birds.

Photo: The status of breeding whimbrel was assessed as being Critically Endangered in Britain as the population has declined by an estimated 81% over the last three generations (27 years), by Mark Eaton