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Shetland Islands, ScotlandOn a narrow isthmus connecting two of the United Kingdom’s northern isles of Shetland, a miserable-looking bird sits hunched on the sand, ignoring people walking by. It’s a new sign of trouble that only recently arrived.

The young gull’s gray and white speckled feathers get blown by the wind, and it makes no attempt to shift to a more comfortable position. With exhausted blinks, it dips and droops its beak toward the sand.

This great black-backed gull would have grown up to be one the biggest of all the gulls, growing its adult-size wingspan to over five and a half feet. But it will never again soar above the North Atlantic.

The same goes for the dozens of gannets lying along this beach, and uncounted corpses across the archipelago. There’s no mistaking them for sleeping birds. They lie like fallen angels might, head flung back, wings splayed, one blueberry eye staring skyward.

Dead and dying birds like these were what first alerted people to the 2022 outbreak of highly pathogenic avian influenza. Also known as bird flu, the virus making these birds sick can be traced back to a goose farm in China in 1996. Since then, the virus has killed millions of poultry and in the past jumped lethally to humans. Sometime in the last year, a strain of the virus mutated and became even more transmissible. This year’s strain is hitting seabirds especially hard. (See photos of how bird flu affected China.)

“It’s grim,” says Kevin Kelly, Shetland site manager for the Royal Society for the Protection of Birds (RSPB) who’s been witnessing the disaster unfold on the ground.

There is no euthanasia program for suffering birds—there are too many for that. Every week or so, Kelly zips himself into full PPE gear, and gathers and incinerates up to 50 corpses scattered around inland water bodies where live birds gather to bathe. He thinks these corpses could accelerate the spread of the virus. These are a small fraction of all the dead birds across the islands.

Shetland saw some of the earliest outbreaks this year in Europe, possibly brought by waterbirds migrating north toward their breeding grounds in the Arctic. Over the last few months, the list of mass mortalities among wild species has been growing, in particular among breeding colonies where birds cluster in large numbers, from Dalmatian pelicans in Greece and knots in the Netherlands, to Caspian terns on Wisconsin’s Lake Michigan. In July, bird flu was confirmed among unusually high numbers of stranded, dying seals off the coast of Maine.

“It’s definitely a crisis,” Kelly says. “Without a doubt.”

James Pearce-Higgins, director of science at the British Trust for Ornithology, agrees. “We have not seen this level of population impact before,” he says. “It is completely unprecedented.”

Seabird populations that are now being slashed by bird flu are already at risk from a great many other threats. More than half of all seabird species are thought to be in decline, with combined threats of climate change, overfishing of their prey, by-catch in fisheries, and non-native mammalian predators eating their eggs and chicks, such as rats and cats. (Read how we can help seabirds survive a warming world.)

As well as being sentinels of ocean health, seabirds also play vital roles in ecosystems on sea and land. They move essential nutrients in their feces, and as top ocean predators, many seabird species help regulate the rest of the food web.