Scotland’s capercaillie are in trouble. While long-term declines in capercaillie have been documented across continental Europe and Fennoscandia, the overall European population may now be increasing. However, Scotland’s capercaillies appear locked in a continuing downward spiral. This Caledonian population has been lost before, becoming extinct in 1785 (due principally to catastrophic habitat loss), but a successful reintroduction from Swedish stock in the 1830s led to a temporary recovery. As recently as 1970, around 20,000 birds are thought to have occupied Scotland’s woods. However, from this high point, Scotland’s capercaillie have been experiencing a steady decline. The first systematic survey in the winters of ’92/’93 and ’93/’94 recorded just 2200 birds. In 2012, this population estimate was revised down to 1285 birds. Today, some estimates suggest the number has halved again.
Globally, capercaillie declines are believed to be being driven by habitat loss and intensifying land use. Modern forestry and the intensification of agriculture have been problematic for these disturbance-sensitive birds, as have changes in livestock grazing pressure and increases in browsing by wild ungulates, although the precise mechanisms driving declines remain poorly understood. Added to these factors, capercaillie appear vulnerable to climate change and increases in generalist predators. In Scotland, deer fences are also associated with adult mortality, while disturbance from human recreational activity compounds these problems by further reducing available habitat. Capers (pronounced “cappers” in Scotland) appear caught in a perfect storm.
Often these limiting factors and drivers of decline overlap. Wetter springs, linked to anthropogenic climate change, create shortages of insect food – an important source of protein for young chicks – making them more vulnerable to predation. Thus, while predation may be the proximate cause of much caper mortality, the ultimate cause may be habitat degradation, mesopredator release (increases in medium-sized carnivores freed from suppression by exterminated apex predators) and climate change, all linked to human activity. As few as 500 capers may now survive in Scotland, often in isolated subpopulations reduced to a handful of individuals. The question of what is driving their decline is not only academic. It is now an urgent question of life and death, of survival versus local extinction.
You might imagine that such a grave situation would motivate conservationists to pull together, to act with the urgency and decisiveness needed, but instead the Scottish capers’ predicament has brought to a head a larger debate about how Scotland’s wildlife and wild places should best be conserved. Specifically, it has pitched the interventionist approach of traditional conservation against the preferred hands-off, or at least, minimal interventions preferred by rewilders, with the crux of the question being what to do about the pine marten problem.
Pine martens are a medium-sized mustelid, like a super-sized stoat grown to the size of a house cat. They were historically persecuted by gamekeepers, being completely exterminated in England, except for sporadic, isolated reports, and this history of persecution undoubtedly informs much of the concern elicited now by talk of controlling pine martens once again. By the late 20th century, British pine martens were largely confined to a few remote refugia in the North and West of Scotland. However, in recent years they have benefitted from formal protection, staging a slow but steady comeback. Pine martens have also been reintroduced in some areas, including in Dumfries and Galloway, Wales and South-West England. They can now be found across the Highlands and are gradually pushing south and into the borders. But while this is an undoubted conservation success story, the resurgence of these agile generalist predators has also been identified as a potential problem for capers, raising the question of what to do when one protected species threatens another.
This is not a unique situation, and is a symptom of disturbed ecosystems undergoing recovery. The question though, is what to do about it. There is evidence that pine martens are significant nest predators of capercaillie and so removing pine martens might help capers. Conversely, not removing pine martens might mean missing an opportunity to prevent the capers’ demise. Those in favour of removal point to its success in yielding gains for capercaillie in the Pyrenees. More generally, predator culls are a recognised tool in the conservation tool kit, especially when problematic predators are non-native or pose a threat to small, vulnerable populations. But they are also controversial. Many question the ethics of culling programmes that do not have an exit plan. Others question the true efficacy of such culls. Indeed, in the case of capercaillie, there is some evidence that such culls offer only limited, short-term effects in determining population trends.
Against this contested backdrop, NatureScot recently completed a review of which measures might help halt the decline of Scottish capercaillie, concluding that: “predation is a significant contributor to variation in breeding success. Increases in some nest predators (notably the pine marten) in recent years are likely to be contributing to the decline in capercaillie breeding success and hence population size.” The review stopped short of recommending lethal control of what remains a protected species, but concluded that live trapping and removal of pine martens (for translocation) should at least be considered.
Unsurprisingly, this review has stimulated some pushback. The RSPB published a detailed blog, stating that the review was welcome and that they were in broad agreement with much of it, but questioning what they characterised as an “over-emphasis of the importance of evidence underpinning predation and predator control, and under-emphasis of the impacts of climate change and habitat management.” They argue that much of the evidence cited in the report is old, and were at special pains to point out that at the RSPB’s Abernethy Reserve, where no predator control has been conducted in recent years, capercaillie breeding numbers appear to be holding steady, even as they have continued to decline almost everywhere else in Scotland. If predators are the key problem, why then, they argue, are capers continuing to disappear from heavily keepered areas of Deeside and Perthshire, while remaining stable in the forests of Abernethy?
It’s an important question, but perhaps also a trifle disingenuous. Not everywhere is Abernethy, contiguous with the hundreds of square kilometres of wild land that make up Cairngorms Connect. In smaller, more isolated habitat patches which yet support small numbers of capercaiilie, predator culls and pine marten removals may offer a means to protect these most vulnerable birds, at least in the short term, until their fragmented habitat islands can be joined up to more extensive tracts of contiguous woodland. However, where there is no plan or prospect of such a possibility, the justification for such measures appears significantly weaker. As Richard Mason, Abernethy Conservation Manager for RSPB Scotland, has noted:
“Predator control has failed to prevent decline of capercaillie across Scotland. We don’t think the solution is to start killing other predator species, but to restore habitats and rebuild more functional predator populations. The return of pine marten, white-tailed eagles and goshawks to our forests is a great success story and the discussion now should be about how to further restore naturally functioning forest ecology, not to dismantle it again.”
Habitat restoration and the recovery of functional ecosystems undoubtedly offers the best long term solution. But in the here and now, there is one other important consideration. If rewilding advocates are too dogmatic in insisting that pine martens are sacrosanct and cannot be interfered with, they risk doing wider damage to their longer term goals. Critics question why rewilders are happy to cull deer, but not predators, to interfere in some ways but not others. Many consider it irresponsible to allow the capercaillie to go extinct again without exploring all the options. In an apparent rebuke of the RSPB’s position, Patrick Laurie expresses a common perception that:
Many who object to and indeed fear Rewilding express the concern that rewilders want to rewild everywhere. But rewilding is not and never will be appropriate everywhere. Context is vital, both in predicting the likely ecological consequences of rewilding action, and in terms of the communities and situations where rewilding might be considered. Showing some flexibility when it comes to managing pine martens might encourage sceptics to believe that rewilders might be trusted to consider context in the future conflicts imagined in the wake of proposed lynx and beaver releases. Ultimately, in the case of isolated, highly vulnerable caper populations, the risk of a non-interventionist ‘Abernethy approach’ is that it could condemn some capercaillie populations to local extinction. And the legacy of that could tarnish the Scottish rewilding movement forever.