When tourists come Stora Karlso, a limestone-cliff nature reserve off the Swedish coast, keeps a respectful distance from the many sea birds that call the island home. Like most visitors to wild places, they only want to leave footprints and only take photos – to slip between the strands of the web of life they have seen.

No luck. In an article published in Biological Conservation this month, The researchers describe how the sudden absence of tourists on Stora Karlso during the pandemic started a surprising chain reaction that devastated the Murres colony on the island and reduced the population of newborn birds.

Stora Karlso became a nature reserve in the 1880s after thousands of years of human occupation. The common murre population, which previously fell to less than 100 due to hunting and egg hunting, now comprises around 60,000 birds and is the largest in the Baltic Sea.

Jonas Hentati-Sundberg, researcher at the Swedish University of Agricultural Sciences and lead author of the new paper, has been studying the colony for 19 years. When he and his team started planning the 2020 research season, they expected the pandemic to pose logistical hurdles: without visitors, fewer boats would be in operation and the island’s restaurant would close.

“Those were our main thoughts,” he said.

On their first trips of the year at the end of April, however, they found that the Murres “flew away all the time” and that individuals sometimes disappeared for days. It was a change in behavior, he said, and a sign that something was making the birds more nervous than usual.

The island’s sea eagles also changed their behavior. Typically seven or eight eagles spend the winter there and then head out when the visiting season starts in spring, said Dr. Hentati-Sundberg.

Updated

Jan. 22, 2021, 4:59 p.m. ET

But without the influx of tourists, they stayed here and more eagles joined them – sometimes dozens at a time. “They will gather in places where there is plenty to eat and little disturbance to people,” he said. “This year it was her hot spot.”

Further observations made the new dynamic clear: the eagles, freed from the disturbing presence of humans, even disturbed the grumbling.

Although eagles seldom chase murmurs, the seabirds fear them and disperse at the slightest flyby. In a video from May, a distant, broad-winged figure sends hundreds of murmurs, hopping from their ledges and cascading like theatergoers running after the curtain from the balconies.

This happened over and over again. From May 1 to June 4, birds in part of the colony were driven from their nests by eagles an average of 602 minutes a day – far longer than the 2019 average of 72 minutes.

In addition to time, the Murre colony was losing eggs, throwing them off the combs in panic launches, or making them vulnerable to hungry gulls and crows. 26 percent fewer eggs hatched in 2020 than typical for the rest of the decade.

“Emotionally, it’s a bit difficult to chew,” said Dr. Hentati-Sundberg.

Researchers around the world have used pandemic travel restrictions to study the effects of sudden human absence on the natural world, an event that some have called “anthropause”. A finding like this, where tourism disruption has a domino effect in several ways, is “fascinating,” said Nicola Koper, a professor of ecology at the University of Manitoba who was not involved in the research. “This shows how effective our travel changes have been on entire ecosystems.”

For Dr. Hentati-Sundberg emphasized one summer on a changed Stora Karlso how closely we can be interwoven with other species – even if we see ourselves as mere observers – and that “we understand our relationships with nature and accept the idea of ​​ourselves as part of it of the image is a more fruitful strategy ”for conservation decisions.

“Resigning is not an option,” he said. “We’re out there.”