After a Devastating Bird Flu Outbreak, Scotland’s Seabirds Are Slowly Recovering—and So Are the Scientists Who Witnessed Their Decline

Bass Rock, a guano-covered hunk of rock off Scotland’s east coast, boasts the largest northern gannet colony in the world. With steep sides and a rounded top, Bass Rock is prime nesting territory, and in the spring of 2022, tens of thousands of the birds did what they always do—pack the island to lay their eggs and raise their young. But by the end of summer, things had gone horribly wrong. Highly pathogenic avian influenza (HPAI) had reached the island. The result was devastation—for the birds, but also for the researchers who’ve committed decades of their lives to protecting them.

Avian flu comes and goes. Yet since 2020, a new, extremely contagious strain has been ravaging bird populations across the planet. First identified in Europe, this ongoing HPAI outbreak has been killing and debilitating wild and domesticated birds, as well as numerous mammal species. Avian influenza’s effect on seabirds has been especially severe; in the United Kingdom, for example, the breeding population of northern gannets (Morus bassanus) declined by 25 percent, while the roseate tern breeding population fell by 21 percent, according to 2023 counts. The great skua, a large brown seabird, has been particularly hard hit—its breeding population dropped by a dire 76 percent across Scotland after the outbreak.

Jude Lane, a conservation scientist with the U.K.-based Royal Society for the Protection of Birds, first came to Bass Rock in 2015 as a doctoral student and has returned every year since. Usually, she says, a seabird colony is a “very smelly, very noisy” place. With so many birds in tight confines, “it’s basically just filthy. You get Bass Rock in your hair and in your clothes,” she says.

That’s what it was like when Lane traveled to the island in April 2022, at the beginning of the nesting season. Everything seemed normal. Then, in early June, the first gannet on Bass Rock tested positive for HPAI.

“Two weeks later, it was absolutely devastating. It was just so quiet,” says Lane. “I don’t think a seabird colony is ever quiet. But at Bass Rock, it was just eerie.”

By the end of the month, a drone flying over Bass Rock photographed more than 5,000 dead birds. In many cases, these were animals that Lane knew. Years of fieldwork had given her the familiarity to recognize individual birds. “They’d literally sat there and died whilst incubating eggs,” she says. “It was just heartbreaking to see what [the virus] did to them.”

In 2021, before HPAI ripped through, there had been approximately 160,000 gannets on Bass Rock. By 2023, that number had dropped to less than 105,000. Not every gannet that contracts HPAI dies. But Lane and her colleagues noticed that even the birds that recovered were far from unscathed. In fact, many were changed by the infection in a most unexpected way: The irises of their eyes turned from vivid blue to black.

Lane is working with ophthalmologists to understand why this happens and what broader effect, if any, this bizarre transformation has had on the birds. In the meantime, the discovery offers Lane and her colleagues a way to identify gannets that were infected by HPAI and then recovered, so they can track lingering effects.

One recent study led by Lane and Sue Lewis, an ecologist at Scotland’s Edinburgh Napier University, investigated the reproductive success of HPAI survivors compared with birds that were never infected. The good news: There was no difference in fertility between the two groups. The bad news: Reproductive success for the colony is still lower than before the disease ran through, probably due to the loss of so many experienced parents.

Twenty years ago, Lewis studied the Bass Rock gannets for her doctoral research. She stopped doing fieldwork around 2007, once she began teaching and started a family, but she still checks in to collect data on how the gannets are doing using remote cameras operated by a charity called the Scottish Seabird Center. Lewis’ scheduled observation window overlaps with breakfast time in her own home, and she likes to watch the birds from her kitchen table while her kids are getting ready for school. If a bird gets ornery and begins pecking at its neighbor, “I start shouting at them through the screen,” she admits. Even from a distance, watching the HPAI outbreak unfold was “absolutely gutting,” Lewis says.

Hope, Lewis admits, is not a scientific concept. But right now, hope is what keeps her going. “I just keep thinking, ‘Next year, will breeding success be up a bit?’ And hoping that that does happen.”

Johanna Harvey, an HPAI expert at the University of Rhode Island who is not involved in studying Bass Rock’s birds, worries that as the global HPAI outbreak drags on, people will become complacent.

“It’s such a dynamic disease that evolves very quickly, and this current clade of virus that has spread globally has thrown us a lot of curveballs,” Harvey says. “It’s still very much happening and very much evolving.”

HPAI is just the latest in the long list of threats faced by seabird populations, which also includes climate change, overfishing and offshore wind development. For now, Lane and the other researchers studying Bass Rock’s northern gannets are taking it one year at a time.

Unlike some other threats, researchers witnessed HPAI claim its victims firsthand, and it was a visceral experience they’ll never forget. To cope with such scenes of suffering, Lewis, Lane and other scientists are collecting as much data as possible. Their hope is that by learning as much as they can now, they will be better able to help the species they love in the future.

This story originally appeared in bioGraphic, an independent magazine about nature and regeneration powered by the California Academy of Sciences.