Public Release: 12-May-2016
[font face=Serif][font size=5]How Arctic spring kills birds in Africa[/font]
[font size=4]Biologists learned that an early Arctic spring provokes deaths of birds in Africa[/font]

Lomonosov Moscow State University

[font size=3]Having analyzed the data collected for more than three decades, scientists managed to show that the effects of climate changes in the Arctic may come out on a completely different continent, a few thousand kilometers away from the Arctic ice. One of the authors, Eldar Rahimberdiev, researcher at the Biological faculty of MSU, says that the work is unique, as earlier scholars did not consider these problems so complex.

This article considers a small bird of the suborder waders -- red knot (Calidris canutus). This bright red in summer and almost white in winter bird is one of a record-breakers for distance flight, being able to cover about 5000 kilometers non-stop. Every year in the autumn it flies to winter at the coast of Mauritania (or, depending on the subspecies, Australia or South America), and in the spring returns to breed on Taimyr peninsula -- the northernmost mainland of Eurasia (or, again, depending on the subspecies, Greenland, Alaska and the Canadian Arctic archipelago). And then the bird has another record, choosing the most northern and cold nesting latitudes. The arrival of the red knots to these severe lands was "calculated" by evolution so that the birth of the chicks happens just at the peak of abundance of insects, their main food.

But that was before the global warming has seriously changed the lives of the birds within a few decades. These changes are described in the new article. At the disposal of the researchers was a data archive for 33 years, which included complete measurement by Polish scientists on the morphology changes in 1990 juvenile birds who committed intermediate stops in Poland within this period, and satellite images of the Taimyr Peninsula and the results of the Dutch zoologists' observations on the birds at the coasts of Mauritania.

During these 30 years the arrival of spring on the Taimyr Peninsula, and the peak of the insect population moved for almost two weeks earlier in time. If the snow on the peninsula disappeared by the middle of July in the past, it is gone now at the end of June. Arrival dates of birds stayed stable, but phenologically birds begin to nest later than 30 years ago, and miss the peak of insect abundance essential for juvenile growth. The lack of food has caused a decrease in the size of the young birds, which is impossible be compensated later in life. However, at first glance, the problems for birds did not increase: with the arrival of cold weather, young red knots still go to their long journey and still successfully get to Africa, preparing to spend the whole winter there, and fly back only in spring. But the real difficulties come further. During the winter in the Banc d'Arguin National Park in Mauritania, red knots eat bivalve mollusks hiding in the sediment, and they need quite a long bill for reaching this food. Birds with long beaks often diversify their diet with Loripes lucinalis, burrowing deep enough into the sand. Even though that shellfish produces a toxin in their body, in a birds' diet its proportion may be up to 40%. Red knots with a shorter bill reach another food source -- Dosinia isocardia, and those not lucky with the length of the beak are to be fed with plant food -- small rhizomes of Zostera (Zostera noltii). Survival rate of the birds that are not able to get to mollusks Loripes was significantly lower than those which were not restricted in their diet.

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