The great thawing of the Arctic, at three times the pace of anywhere else on the planet, has turned its natural world upside-down. Among wildfowl and wading shorebirds that have “always” migrated between breeding in an Arctic summer and wintering in Ireland, the black-and-white barnacle goose has made a dramatic change in behaviour.
It’s been more than 30 years since I joined an expedition, led by ornithologist David Cabot, to visit breeding geese in the High Arctic wilderness of northeast Greenland. The flocks of barnacles that winter on the windswept Inishkea islands off north Mayo have been Dr Cabot’s lifelong study, and he hoped to find some he had ringed among those arriving at a still-frozen fiord at the end of May.
There they undertook the strategy that has long made these geese remarkable — choosing to nest on narrow ledges high on precipitous cliffs.
This kept the adults safe from predatory Arctic foxes while the eggs were laid and hatched. But the chicks had eventually to feed. This demanded that they jump and fall, fluttering, to the valley floor.
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They often bounced on the way, sometimes fatally, and the foxes were waiting to snap them up. (Cabot filmed this for RTÉ.) Only half survived to follow their parents to the safety of a nearby lake.
There had to be a better way, it seemed, and climate change may have forced them to find it. The geese have long interrupted their spring journey north with a spell of feeding in Iceland. Why not just stay on there and save the annual effort of flying 3,000km to Greenland and back?
This is now happening, in ever increasing numbers. The birds began nesting on Skumey, a glacial lake island, in 2014. Now farmers next to marshlands in southeast Iceland complain that the summer geese have reduced their hay crop by 24 per cent.
By spring 2019 the Skumey nests had increased to 1,330. Hundreds more outside of the lake brought the breeding total to 2,051, with another 4,900 non-breeding adults. This all warranted study, most recently by Dr Cabot, with Susan Doyle, Paddy Manley and Courtney Redmond.
Few predators
In Iceland last month, the team was struck by how few predators were troubling the ground-nesting geese. Repeated visits to their colonies saw only a few isolated attacks by the Arctic skua and great black-backed gull. And while Iceland has some 8,000 Arctic foxes, many in a large nature reserve, none appeared during the lengthy watches.
Indeed, while some barnacles continue to nest in northeast Greenland, those in Iceland show much better breeding success. The High Arctic nesters arrive to find that climate change has advanced the spring thaw and the brief plant-growing season by several weeks. By July the goslings can find the protein of their food grasses in decline.
This mismatch, now disturbingly familiar in the progress of climate change, features also in the breeding of migrant shorebirds.
A report by the Cabot team cites seven years of American research in Alaska to study the impact of earlier snowmelt on the nutrition of waders such as dunlin and sandpipers. It found that only about half their chicks were getting enough insects. Unless the birds can match their nesting to the Arctic’s advancing warming, their future populations could dwindle.
A warming world could, indeed, change whole migration strategies, as with the barnacle geese. A Nasa analysis of more than 200 studies, tracking more than 100 species since 1991, found the movements of Arctic animals shifting in different ways, which could disrupt entire ecosystems.
The numbers of migrant caribou are already in decline, as their calving, cued by length of day, fails to match the new season for plants, leaving their young short of nutrients in their summer food.
Cabot’s team will repeat their Iceland study next June. Meanwhile, many of last winter’s barnacle geese on the Sligo coast were early, fatal victims of the bird flu now sweeping colonies of nesting seabirds, notably around Scotland. They include the birds of the Bass Rock, the world’s biggest gannetry.
This plague of avian influenza has spread to wild birds from the intensive poultry industry in China, and thrives among the seabirds ranked wing to wing on the ledges of cliffs and islands. Since species will undoubtedly survive and recover, the flu could be seen as a natural control on avian populations. How long before Covid-19 and its successors are granted similar accord in the natural regulation of Homo sapiens?