Today, we are publishing the 5th review of ‘Birds of Conservation Concern’, commonly referred to as BoCC, in the journal British Birds. This was a partnership project between the RSPB, British Trust for Ornithology, Game & Wildlife Conservation Trust and the government agencies - Joint Nature Conservation Committee, NatureScot, Natural England, Natural Resources Wales and Northern Ireland Environment Agency.

Swifts in flight (c) Ben Andrew (rspb-images.com)

What is ‘Birds of Conservation Concern’?

BoCC is a well-established, well-respected process for identifying conservation priorities for birds in the UK, Channel Islands and Isle of Man. It uses quantitative assessments against standardised criteria to allocate species into one of three lists, ‘Red’, ‘Amber’ or ‘Green’, depending on their level of conservation concern; with those that have either suffered severe declines, or are threatened with global extinction, appearing on the Red list of species of high conservation concern. The first review to use this traffic light system was published in 1996. Since the it has been repeated, roughly every six years. This represents the 5th edition or BoCC5.

It is well recognised that the UK’s wildlife is in trouble and previous BoCCs have documented the declining status of our bird populations, with an ever-increasing Red list. They have helped to highlight the plight of the widespread decline of farmland, woodland and upland birds, as well as our summer migrants. These reviews have, however, also showcased conservation success stories, such as the recovery, or partial recovery, of some raptor species (marsh harrier, red kite, osprey), stone-curlew, bittern and Dartford warbler.

What has BoCC5 shown us

BoCC5 again adds to the wealth of existing evidence that show many of our bird populations are under threat. Shockingly, this review shows further declines in the status of our regularly occurring species and we have placed more species (70) on the Red list that ever before. This is almost DOUBLE that recorded in BoCC1 25 years ago.

Length of the Red, Amber and Green lists across the five BoCC reviews. Note that the assessment process has developed over time and this figure does not take account of changes to criteria, taxonomy or species joining or being omitted. Some changes in Red, Amber and Green list lengths have been as a consequence of these changes.

Since the last review in 2015, eleven species move onto the Red list of birds of High Conservation Concern from either the Amber or Green lists, while only six species move the other way, because their status has improved.

Golden oriole, a species that never had more than a toehold in the UK, has now been lost as a regular breeding species. With the last confirmed breeding attempt in 2009, it now moves off the Red list to join the list of other former breeding species, such as wryneck and Kentish plover.

The 11 new Red list species

Ptarmigan, swift, Leach's storm-petrel, purple sandpiper, Montagu's harrier, house martin and greenfinch all move to the Red list because their breeding populations have suffered severe declines (greater 50%). Similarly, Bewick's swan, goldeneye, smew and dunlin, move to the Red list due to severe declines in their non-breeding populations. Leach's storm-petrel is also now classified as being threatened with global extinction.

Photos from top left, rotating clockwise: ptarmigan, house martin, swift (c) Ben Andrews (rspb-images.com) and smew (c) Ben Hall (rspb-images.com)

The six species moving off the Red list to Amber

Song thrush, redwing, pied flycatcher, black redstart and grey wagtail all moving off the Red list to Amber, owing to less severe declines in breeding population; however, both song thrush and pied flycatcher trends (-49.9% and -43.4% respectively) remain close to the Red list threshold (-50%). Although these represent movements in a positive direction, and like species that just exceed a threshold, it is important to acknowledge these changes, but they are not exactly cause for celebration. Both black redstart and redwing remain rare breeders.

Photos from top left, rotating clockwise: song thrush, pied flycatcher, redwing and black redstart (c) Ben Andrews (rspb-images.com)

All previous BoCCs have included aquatic warbler but owing to the exclusion of all species defined as rarities in the UK, this threatened species, formally classed as a scarce migrant, was not assessed in BoCC5.

The stories within BoCC5

Within the picture of overall declines in the status of bird populations, there are particular stories to be told.  The plight of our long-distance Afro-Palearctic migrants that spend our winter in Africa was raised in BoCC3 and 4. We note further declines in the status of this group.

Although the status of species that spend the non-breeding season in the northern arid zone continues to decline (sedge warbler, common whitethroat and northern wheatear all move from Green to Amber list in BoCC5), it is the species that travel down to the humid and southern zones of sub-Saharan Africa which are of higher conservation concern. Two migratory aerial insectivores, swift and house martin both move onto the Red list.

Previous reviews have highlighted the worrying decline in birds associated with farmland, woodland and uplands. There has been no improvement in the overall status of species associated with farmland and upland; indeed, more such species have been Red listed. 

Bird health is becoming an increasing issue. In this review, greenfinch has moved directly from the Green to Red list, due to a dramatic population crash caused by a severe outbreak of trichomonosis. This infection is spread through contaminated food and drinking water, or by birds feeding one another with regurgitated food during the breeding season. Garden owners can help slow transmission rates by temporarily stopping the provision of food if ill birds are seen and making sure that garden bird feeders are cleaned regularly.

Sadly, our chaffinch population appears to be going a similar way, but they don’t currently qualify for any of the BoCC criteria. The exact cause is yet to be determined.

Greenfinch numbers have dropped 62% since 1993 © Ben Hall (rspb-images.com)

We also raise concerns over the status of our wintering wildfowl and wader populations. In BoCC1, no species qualified for the Red list due to their non-breeding trend, but eight species did exceed the threshold in our study. Bewick's swan, goldeneye, smew and dunlin join the Red list for this reason.

Pressures are wide-ranging, from threats on migration, illegal hunting abroad, ingestion of lead ammunition to the impacts of climate change. Assessing drivers are complicated by ‘short-stopping’ whereby species have shifted their wintering grounds north-eastwards in response to increased temperatures caused by climate change.

There is little positive news to come out of BoCC5. The findings reinforce previous reviews, and the key stories are all supported elsewhere. It highlights new species that should now be considered of high conservation concern, such as Leach’s storm-petrel, swift, house martin and greenfinch, but we must not forget the 59 species which remain on the Red list, many of these are continuing to decline.

White-tailed eagle off the Red list

One of the very few positive stories is white-tailed eagle moving off the Red list for the first time. Owing to the recent population increase (now put at 123 territories), the species no longer qualify for the ‘Historical Decline’ criteria and moves to ‘Historical Decline recovering’.

Like the increases in Bittern and Red Kite populations showcased in previous BoCCs, it highlights what can be achieved with dedicated conservation action. Nature conservation needs to become bolder, take place over a greater scale and be much better resourced. It is also vital that we continue to monitor our bird populations and to make regular, periodic updates to our assessments so we can measure progress towards relevant biodiversity targets and refresh our priorities.

White-tailed eagle are now at 123 pairs © Katie Nethercoat (RSPB-images)

Finally, we are extremely fortunate in the UK to have many thousands of dedicated volunteer birdwatchers, coordinated by professional research and conservation organisations, collecting information on our bird populations. We would like to thank all those that have helped to monitor avifauna, without which such assessments would be impossible. This study was funded by RSPB and Natural England as part of the ‘Action for Birds in England’ partnership.

We used the same opportunity to update the IUCN Regional Red List assessment of extinction-risk for Great Britain. Further details of both assessments can be found within the paper.

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