Earlier this month, the South Downs National Park (SDNP) published a press release announcing that it had successfully released 30 turtle doves at a site near Selborne back in the Spring, and is planning to release a further 100 in the same area of Hampshire in the coming years. This announcement was picked up uncritically by national media keen to present this as a feel-good story.
Despite its appearance in a Christmas carol, the turtle dove (Streptopelia turtur) is a summer migrant to Britain, arriving in April to breed in thick scrub, and leaving in late summer and autumn to spend winters in the Sahel, along with the wider European population. It’s likely Britain’s fastest declining bird, with breeding populations here having plummeted by 99 per cent since the late 1960s. It would therefore seem superficially like a good idea to bolster the remaining population with captive bred birds.
Contested by conservation groups
However, this scheme has been contested by Operation Turtle Dove – a partnership between the RSPB, Pensthorpe Conservation Trust and Natural England that aims to reverse turtle dove declines. This group points out that releases of captive bred birds fail to meet IUCN guidelines, stipulating that reintroductions should go ahead only if the threats which caused declines in the species have been addressed, and if there’s sufficient habitat to support the reintroduced population.
There are several major factors behind declining turtle dove populations. Firstly, they’re recreationally hunted in parts of southern Europe along their migration routes, at a level assessed in 2019 to be unsustainable for maintaining a stable population. Based on this and other studies, a moratorium on turtle dove hunting was introduced by the European Commission in 2021. This brought immediate benefits, with estimated numbers along the western migratory flyway increasing by 25 per cent in just two years. Regrettably, the Commission took this tentative increase to mean ‘job done’ and lifted the moratorium last year.
The threat is agricultural intensification
Within Britain, arguably the most important issue, as pointed out by Operation Turtle Dove, is agricultural intensification since the 1960s having reduced the availability of habitat in the form of co-occurring dense scrub nesting sites and seed food during the breeding season. As agriculture has intensified, wildflower meadows have been ploughed up, crop diversity has decreased, pesticide use has increased and scrub and hedgerows have been ripped out at an alarming rate.
Turtle doves are obligate granivores, meaning they traditionally feed mainly on seeds of wildflowers and pioneer plants. After decades of agricultural intensification they’ve become increasingly reliant on farmland seed crops and weeds, which rarely co-occur with thick stands of scrub. This reduction in nest sites and food availability has resulted in a shorter effective breeding season, with pairs now raising only half the number of broods on average compared to the 1960s.
Some efforts have been made recently to address this state of affairs, with the farm subsidy regime being tailored more towards environmental improvement post-Brexit. More sites are now engaging in rewilding or ecological restoration.
Among the best remaining strongholds for turtle doves is the Knepp Wildland in West Sussex. There, the large amount of thorny scrub developed since it began its rewilding project has provided ample nesting and roosting habitat, and it’s thought that the rooting behaviour of their free-roaming Tamworth pigs – a stand-in for wild boar – has enabled a greater diversity of pioneer plants to colonise freshly turned over soil, providing plentiful seeds.
While there are therefore indications of positive changes to land management in some places (including parts of the South Downs), there’s still much to be done to restore turtle dove habitat at scale.
Releases are unnecessary and counterproductive
Simply chucking some captive bred birds into the landscape may provide a short-term boost in absolute numbers but doesn’t equate to sustainable population recovery.
On the contrary, unless there’s a substantial increase in available habitat simultaneously, it may make the problem worse by increasing competition for limited resources – not to mention risks of disease transmission or genetic dilution of the wild population, potentially affecting its fitness and migration patterns.
Moreover, if the threats facing Britain’s breeding turtle doves were sufficiently reduced and there was ample habitat to support them, supplementing the population with the release of captive stock would be unnecessary.
As noted above, turtle doves are long-distance migrants which cross the Sahara and the Mediterranean twice per year. They’re perfectly capable of reaching Britain, and while some recent evidence points to strong breeding-site fidelity in tracked pairs (they return to the same breeding site in successive years), young birds aren’t so faithful to their natal site, so birds hatched on the continent may establish territories here.
In other words, the population would recover naturally given favourable conditions.
This contrasts with successful reintroductions of species like red kites, which were wiped out in most of Britain due to historic persecution which has greatly reduced in modern times, and which are generalist scavengers without such specific habitat requirements. Red kites are non-migratory and have low dispersal distances, so probably wouldn’t have recolonised Britain naturally.
Releases of turtle doves in the South Downs – especially given the number of breeding territories a few miles north at Knepp and relatively high numbers in Sussex more widely – are therefore unnecessary at best, and potentially counterproductive. Doubtless they are well-intentioned, but like Defra’s recent announcement of funding for golden eagle reintroduction in England, they appear to be motivated more by PR than conservation evidence.
It’s notable that the partnership coordinating the releases, led by the National Park Authority, includes no scientific or wildlife conservation organisations.
When it comes to recovering our biodiversity, we can’t rest our hopes on such short cuts.
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