Tracking trouble in the Arctic

Migrating shorebirds face a long list of hazards on their epic flights

Many shorebird populations are declining steeply around the globe, and those that nest in the Arctic are among the hardest hit. On their long-distance migrations, they encounter a number of threats, including hurricanes and hunters, pesticides in croplands and human sprawl that is destroying wetlands used by the birds as refuelling stations. By tracking the journeys of each species, researchers can better understand the problems confronting these birds.

Shorebirds are vulnerable because their migrations are tightly tuned to the cycles of other species. The robin-sized red knot (Calidris canutus, pictured) that breeds in the Canadian Arctic times its northward migration so that it can stop and bulk up on the eggs of horseshoe crabs (Limulus polyphemus) in Delaware Bay. Western sandpipers (Calidris mauri) touch down every spring on Canada’s west coast to feast on biofilm produced by algae along the expansive mudflats of the Fraser River delta. And all the Arctic breeders aim to have their chicks hatch at a time when there is a banquet of mosquitoes and other insects on the tundra.

But there is growing concern — and evidence — that the connections have begun to fray because of climate change and other human impacts on the environment and ecosystems.

Illustration: Emily Cooper

Sources: goose population, ref. 4; Motus towers, Stuart Mackenzie; bird flight paths, Sjoerd Duijns

Sources: population-decline data, Adam Smith & ref. 1; stolen-egg data, Paul Smith

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