Warming oceans may have been behind the deaths of seabirds on both coasts of North America this year.
Nearly 90 percent of Atlantic Puffin chicks that hatched on Machias Seal Island in the Gulf of Maine perished this summer. The island is home to about 5,500 pairs of puffins, and each pair lays only a single egg. Normally, about 60 percent of the nests produce young that survive. This year, the tally was only 12 percent, and scientists say the fledglings were in poor condition.
The mortality was due to a food shortage. The usual fish species that adults feed their young were not available in adequate numbers. The fish either shifted their ranges or moved to deeper, cooler water below the puffins’ diving limit. The fish were likely responding to water temperatures that were the second warmest on record.
Fortunately, survivorship was better on islands west of Machias Seal that host smaller colonies. Adults on each island have their own fishing grounds. Birds with higher success had access to fish that were less nutritious than their traditional prey but were nonetheless better than the options available to the Machias Seal puffins.
Meanwhile, in the waters north of Washington’s Olympic Peninsula, at least 30 Rhinoceros Auklets were found dead this summer. In a typical year, only one or two are reported.
Federal investigators said the birds had no fat and had likely starved. The deaths were attributed to unusually warm water in the North Pacific and the displacement of forage fish — similar to what happened in the Gulf of Maine. Although the water is cooler this year than in the past two years, when other die-offs occurred, temperatures are still above normal, and food chains may not have recovered yet. — Julie Craves
A version of this article appeared in the December 2016 issue of BirdWatching.
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