This year, scientists searching for Caspian terns in the parts of Alaska where the coastal species normally nests were out of luck. The birds were 1,000 miles to the north.

In 2016, Alaska's Caspian terns abandoned their normal breeding grounds for beaches inside the Arctic Circle. This year's nesting site is 1,000 miles farther north than any previously documented site.

A team of scientists with the Wildlife Conservation Society monitored the site in August, observing as a group of chicks were reared along the coast of the Chukchi Sea.

The Caspian tern is the largest tern species. The shorebirds are found all over the world, but until this summer, they hadn't been found nesting farther north than Neragon Island in the south Bering Sea.

Global warming is happening everywhere, but its effects are most dramatic close to the poles. In the Arctic, long stable migration patterns of a variety of animals have become sporadic and increasingly driven by unusually warm temperatures.

Summer is getting longer and expanding northward, allowing many temperate species to expand into previously uncharted territories.

"What we saw this season for Caspian terns is another example of the fragility of the Arctic system," Peter Zahler, WCS regional director, said in a news release. "New patterns are starting to take hold in an environment that is dynamic and reinventing itself in the context of a new warmer climate."

"However, the arrivals of new species are mirrored by the challenges for existing ones adapting to new conditions such as walrus and polar bear," Zahler added.

Zahler and his colleagues at WCS say continued monitoring of Arctic species is key to understanding how to manage and protect wildlife in a rapidly changing climate.