RUFA RED KNOT

HABITAT Annual migration from the southernmost tip of South America to the central Canadian Arctic THREAT Food scarcity

This small, robin-size shorebird flies 19,000 miles per year in its sweeping migration from Tierra del Fuego, at the very tip of South America, to the Canadian Arctic tundra, where it breeds, and then back again. To fuel this epic journey, the knot carefully times its spring break with horseshoecrab mating season in the Delaware Bay, where it stops to feed on the crabs’ pebble-like eggs, doubling its weight in the process. But warmer temperatures are now prompting horseshoe

crabs, already struggling due to overfishing, to lay their eggs earlier in the year. By the time the knots arrive, they’re left with scraps. And the crab-egg feast isn’t the only meal these birds are missing: In Virginia, rising ocean acidity is depleting the population of blue mussels that knots feed on, and in the Arctic, warmer temperatures are causing insects to hatch earlier, depriving knot chicks of their first meals. In 2014, after its population bottomed out at just 12,000

birds, the rufa red knot was listed under the Endangered Species Act, the first bird to have climate change named as its “primary threat.” According to the National Audubon Society, two-thirds of North American birds are threatened from global temperature rise. “Birds are important indicator species,” said Audubon’s director of climate watch, Brooke Bateman, in a report on the study, “because if an ecosystem is broken for birds, it is or soon will be for people too.”