The flycatcher and COP26

As COP26 draws to a close, with little hope for a real transformation of our ways of doing things, let’s take a look at past climates and their impacts on wildlife. We are living in the Quaternary Era, which began 2.58 million years ago; a straw in the history of the Earth, but a period with a particularly tormented climate: no less than 50 climatic oscillations of varying magnitude and duration, and between 8 and 10 ice ages in the last 800 000 years alone. Many of the species we see, including the smallest birds, existed millions of years ago. I find it absolutely fascinating that they have come through all these crises, adapting to dramatically changed temperatures and landscapes.

This is what colleagues have shown in a recent study led by Vera Warmuth from the University of Munich (1). The scientists looked at the genetics of the black flycatcher, a passerine bird weighing about ten grams and smaller than my hand, which nests in forests, parks and gardens in Eurasia, feeding on insects. The research team determined the DNA mutations in different flycatcher populations from Spain to Norway. The frequency of these mutations allowed them to date the exact moment when these populations split from each other. They found that these divergences correspond closely to major climatic events, including global temperature fluctuations sometimes exceeding ten degrees.

This was the case approximately 130,000 years ago, with an abrupt period of cooling that turned European forests into tundra and damaged flycatcher populations. At the end of this episode, around 110,000 years ago, flycatchers recolonised the spaces that were once again habitable, with distinct populations in the Iberian Peninsula compared to the rest of Europe. This early differentiation of Iberian flycatchers is surprising, as it was previously thought that it only appeared after the very last ice age, some ten thousand years ago. As Jacques Blondel, a specialist in the evolution of birds at the CNRS, confirms, “today’s biodiversity is a legacy of the climatic oscillations that have punctuated the last two million years. The study by Warmuth and colleagues has the great merit of specifying the tempo and mode of this differentiation with the help of a precise example.

The flycatchers in my area are currently wintering in sub-Saharan Africa and I cannot ask them about the posturing of COP26. It is highly likely that the ongoing warming will again transform their ranges and affect their population sizes. Recent studies show that it is already disrupting their migration, forcing them to return to Europe about ten days earlier (2). In their nesting areas, they will find landscapes devastated by intensive agriculture and modern forestry, where the insects essential to their survival are becoming rare.

(1) Warmuth, Vera M., et al. (2021) “Major population splits coincide with episodes of rapid climate change in a forest-dependent bird”. Proceedings of the Royal Society B. 288.1962: 20211066.

(2) Helm, Barbara, et al. (2019) “Evolutionary response to climate change in migratory pied flycatchers”. Current Biology 29.21: 3714-3719.

Environmental chronicle : The snow bunting, feathered flake

As every year since 2004, our team from the CNRS and the French Polar Institute Paul-Emile Victor has been on the east coast of Greenland, in Ukaleqarteq, to study the animals (end). Today, the snow bunting.

At 4 a.m. they wake me up again. I can hear their little paws drumming above my head. Although they weigh only 35 grams, they make a hell of a racket. A whole family of snow buntings is hunting for insects and spiders in the permanent Arctic summer sun. Around 4 a.m. the sun comes out from behind the mountain and warms the dark shingled roof of our Greenlandic hut.

This sudden rise in temperature animates the invertebrates, which the buntings chase frantically. Several groups of four or five youngsters are accompanied by their mothers, from whom the youngsters beg for food with loud chirps.

The young buntings were born two weeks earlier in a rock crevice, a nest carefully chosen by their parents to be out of reach of ermines and foxes. These highly secure quarters are rare, and the males return from migration as early as April to guard their chosen nest and wait for the previous year’s mate.

They then face near-winter conditions, with temperatures often close to -30°C and blizzards that completely cover the birds huddled in the wind. They move around and rest in small groups but, unlike the penguins in Antarctica, they do not huddle together to better cope with the cold: they prefer to shiver, lying in the snow or in a rocky crevice, a few dozen centimetres apart.

Incredible buntings, which alone among the passerines (1) have managed to colonise the very high latitudes in the north of the globe. They nest all along the coasts of the Arctic as far north as Greenland, thanks to an extraordinary metabolism and sometimes a little help from humanity. In the cold, the buntings come close to the houses, to take advantage of the bread crumbs but also to peck at the grasses that surround the Inuit villages.

This vegetation is fertilised by the faeces of the inhabitants and the sled dogs, which are themselves mainly fed with the products of hunting marine mammals, birds and fish. Indirectly, some snow buntings are thus saved from the polar cold by the abundant marine resources of the Arctic.

These buntings, satisfied with the service, spend the whole winter in Greenland. The others migrate from West Greenland to the Great Lakes region of North America, or from East Greenland to the northern Caspian Sea in Russia. These long-distance journeys are made at high altitude and at night, using the Earth’s magnetic field as a compass. But navigation is not without its faults and some get lost, like this beautiful male that appeared in the Chausey Islands (Normandy) in the spring of 1994, which was already calling me towards Greenland.

(1) Small birds belonging to the order Passeriformes, which includes more than half of the 10,000 bird species.

Environmental chronicle

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