A knot in the snow.
Photo: Peter Prokosch
Migratory sandpipers and snow on the Arctic tundra
Snow very much determines the distribution of Arctic birds. In the spring, 24-hour daylight
and vast food supplies attract billions of waterbirds to migrate from virtually all corners of the
world to breed in the Arctic. These migratory waterbirds need snow-free patches to feed and
nest in the tundra.
For sandpipers breeding in Greenland and Arctic Canada, such as the knot, dunlin and sand-
erling, both the density and timing of breeding have been shown to be strongly related to
snow cover. Successful breeding for these birds depends on finding a nesting area with the
right size of snow-free patches and timing breeding so that the chick-rearing period in July
coincides with the emergence of insects. Breeding too early can mean losing the clutch due to
adverse weather events or due to predation by Arctic foxes, which prey more easily on nests in
small snow-free patches. In Siberia, researchers found that, while patch size does not matter
for the well-camouflaged ptarmigan, breeding density of passerines and sandpipers increases
strongly with the size of the snow-free patches.
The highest density of breeding sandpipers is found in central-eastern Greenland, where con-
tinental climate conditions provide an ideal balance between snow-free patches and suitable
vegetation. In the northern-most part of Greenland, the vegetation is thinner and fewer sand-
pipers breed. Further south the conditions are different again. The Atlantic climate, with more
snow, allows only late breeding. Large areas in the Arctic do not harbour any sandpipers at all,
due to greater snow depth and later thawing. If the current observed trend of increased snow
fall continues, the best breeding areas in Greenland will shift further north and push more
and more birds to the edge, with a smaller window for breeding. The most affected species
are those that breed in the high Arctic. In northern Europe, most of Siberia, and Alaska, earlier
thawing will mean more snow-free patches and more favourable conditions for sandpiper
breeding at lower latitudes.
Sources: Meltofte 1985
51
, Rysgaard and others 2003
52
, Summers and Underhill 1996
53
CHAPTER 4 SNOW 49
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