The Stora Karlsö’s bird-watching rebel

28 May, 2021

Watch our video report from Stora Karlsö here

– Do people like to read stuff like this… personal portraits? Oh, they do. yes, I don’t know, I don’t read that stuff myself.

Jonas Hentati Sundberg is a marine biologist and researcher at the Swedish University of Agricultural Sciences. He sits down on a white wooden chair out on the rock shelf on Stora Karlsö, an island located between Gotland and the mainland. The green grass, as green as it can only be at the beginning of summer, gives way to the wind. The landscape here is more reminiscent of the south of France than Sweden.

We have sat down at the highest point on Stora Karlsö. A few meters behind Jonas’ chair back, the limestone cliff ends. Then you are met by a devil’s gap, which extends 40 meters down, until the mountain meets the white pebble beach. The Baltic Sea looks turquoise, like the Mediterranean, on the shore, but then shifts to dark blue. The clouds reflect in the surface.

“Don’t just sit back,” I say.

– Haha, no, I won’t. Once I lay here at the cliff ledge, strapped with a harness, looking out over the edge with binoculars. But I was so excited that I dropped my binoculars down over the edge. I found it down on the beach a month or so later. It was unusable.

Jonas brings his index finger to his nose and pushes his glasses higher up his nose bone. Around the neck hangs a new pair of binoculars, fixed in a leather strap. Suddenly he gets up, brings his eyecups to his glasses.

– Sorry, but now I have to… I think I see…

He points out to the horizon.

– Yep, exactly: that’s a sea eagle! Wonder if it will come here and scare up the guillemots? no, now it’s giving way. Oh well, it was an old one. It just scouts a little bit. It is the younger ones who come in to test new hunting techniques.

He reaches over to me. Indeed, there on the horizon is an eagle.

Behind Jonas’ chair back, brownish-white guillemots howl.

“The guillemots are a bit like penguins, they stand and incubate their eggs and also only get one egg at a time. They are a bit similar in appearance as well, despite not being related to penguins. The guillemots belong to a parallel group called alder birds and the guillemots, unlike the penguins, can still fly. Even if they’re pretty lousy at it.

Photo: Leif Eiranson

The guillemots sit tightly packed next to each other on rock ledges that line up all the way down to the pebble beach. According to Jonas, each guillemot has a square decimeter at its disposal. If some new pig flies up on the shelf, it crash-lands into the others. It looks clumsy, but at the same time, these birds are perhaps one of the most impressive species of animals there is.

“Guillemots are just on the verge of being able to fly to be able to swim so deep at the same time. Guillemots dive and fly, thus using their wings, in the water as they swim. They can dive down to 70 meters to catch a single sprat. There is no other bird with flight ability that can dive so deep.

On the rock shelves sit only the established, older guillemot. The teenagers get to sit on stone islands by the shore.

“It’s a bit like Södermalm – it’s hard to get a home here. No new guillemots move to Stora Karlsö, there may be those who move out into the countryside to other colonies, we have received reports of this. But no new guillemots moves here, probably because there is so little space.

On Stora Karlsö, the guillemots have been around for centuries. But for a period of time they were disappearing. During the 1800s, the guillemots were hunted so intensively that they were becoming extinct, until the company Jagt- och Djurskyddsförenings bought the island in 1877. Then the hunting of birds was banned and Stora Karlsö became a nature reserve. The second oldest in the world, after Yellowstone in the United States.

Today there are tens of thousands of guillemots on Stora Karlsö, but also many other birds. Here you will find, among other things, one of Europe’s densest house martin colonies. Among the guillemots, even tordmular crowds. On the other side of the island you will find cormorants and sea eagles. Some eiders lie basking in the water. For the past 19 years, Jonas has also been here, at least two months a year. Otherwise, he finds himself in Lysekil, where he works and lives.

Photo: Fanny Jönsson

International attention for their research

– Do you want me to have my hair down when you interview me by the way? The BBC wanted me to have it released so they could cut however they wanted. I don’t know stuff like this, but tell me what to do.

In his hand, Jonas fiddles with a tassel. It is noticeable that he is medie-savvy. In 2020, together with colleagues Per-Arvid Berglund, Aron Hejdström and Olof Olsson, he published the research report ” COVID-19 lockdown reveals tourists as seabird guardians” in Biological Conservation. The report was about how the guillemots on Stora Karlsö were affected by the pandemic. The result: The guillemots became fewer.

“We were lucky to be able to come out here and continue our research, even though the island was closed to tourists. It was perhaps my most exciting field season here.

Out on the mountain, the researchers, with the support of wwf, have built an artificial rock shelf that they can climb down to look at the guillemots without disturbing them. There they have also installed surveillance cameras so that they can film the birds during all hours of the day. But last year Jonas noticed that something was different about the guillemots, they did not behave as usual.

“They were more worried than they are otherwise and sometimes they would leave the cliff shelf without us understanding why.

The cameras gave them the answer. It turned out that from time to time, at dawn, calabash erupted in the pig colony. Wind by wave, the guillemots left the shelf and their eggs. Some of the eggs fell off the shelf or were taken by hungry thrushes or crows.

“We started to wonder what it was that scared them like that? They haven’t been like that in previous years. So we started looking more carefully at the clips. In parallel with that discovery, we noticed that there was an unusual amount of sea eagles on the island. Then we saw a sea eagle sweeping by on one of the cameras and thought: maybe there’s a connection here.

Jonas and his colleagues initiated a study. They began to count on the eagles on the island, as well as how often the guillemots were frightened in comparison with previous years. It turned out that sea eagles had increased by 700 percent since the year before. And by as many percent, the disturbance of the guillemots also increased.

“It’s a number that you only dream of discovering as a researcher. 700 percent on both sides.

In 2020, the guillemots received 26 percent fewer eggs than they had received per year in the past decade. Not that the eagles necessarily ate the guillemots, the researchers never saw an eagle take a pig’s nest, but the presence of the sea eagles affected the guillemots so much that they simply left the shelf for fear and thus abandoned their eggs. Like other birds back then, they took the opportunity to eat up.

The guillemots are frightened by a sea eagle flying along the cliff shelf. In 2020, the presence of sea eagles on Stora Karlsö increased by 700 percent.
Video from J. Dentati-Sundberg et al., Biological Conservation 2021

“It was hard to see that the guillemots were affected, but at the same time it had almost become a bit tedious to do research here. It kind of went too well – the guillemots have only felt better and increased in number since I started my research. What happened last year put everything in a new perspective. It is not a given that the guillemots feel good.

Today, scientists say that the Earth is in a geological age known as the Anthropocene. The title describes how human actions now have such a great effect on the ecosystem that it changes the entire ecological balance. But in 2020, when the pandemic’s restrictions hit, the researchers saw how many human activities stopped and we temporarily ended up in an antro break, i.e. a break from the Anthropocene. The general picture was that nature might now have a chance to feel good again, when people disappeared.

“I think a lot of people have an idea that everything we do as humans has a negative impact on nature. But it doesn’t have to be that way and so did our study. Sometimes we have a positive impact on nature, like here on Stora Karlsö. Our invisible hand is everywhere and we cannot “take a step back” from nature as we may have previously thought. We are already part of the ecosystem, whether we are physically on site or not.

Dropped out of high school to become a guide

Jonas spent his first years of life in Stockholm and moved to Gotland at the same time as he started school. But the school’s framework was too tight for Jonas. That’s why he dropped out of high school at 17.

“I was a bit of a rebel. I thought I was above certain rules and had a lot of thoughts about the hierarchy of the school. At the end of my school days, I argued with several teachers. When I think back, I can see that I was quite arrogant. Once I dropped out of high school, I pulled here and became a bit of a mascot among established guides, biologists and overseers. Then they asked if I wanted to be a guide and now I’m here. But it wasn’t a given that it was birding that was going to be my career, it might as well have been the music.


“Yes, I play the violin. My specialty is Gotlandic folk music. I can’t play as many songs as most people recognize, but I know a lot of Gotland folk songs.

Jonas laughs. It seems to be a theme for him to snowball into specific areas of what he does. At home in Lysekil, he has a lush garden filled with unique exotic plants. He says he has a lot of interests, but in the role of researcher he has found a home.

“I dream of getting students with the attitude that I used to have. It would have been fun to tutor such a person with such frustration. Today, many young people have a dystopian worldview, which I myself did not have at all at their age.

He believes that the new generation’s curiosity about what the research role entails is something the older generation needs to manage.

“I think we need to find a new way of looking at our research role. In the past, you’ve done your research, then you hand it over to decision-makers and say, “Here’s our data. Now make a decision.” I don’t think we can do that anymore.

He believes that the research is not neutral. In a way, everything is based on a premise.

“Take climate and environmental research, for example, it still assumes that something may not be right. To do research on something like this, it takes commitment, almost a mania to be able to continue and question what you are doing. But then it’s about questioning your own theses and that’s where you as a researcher have a responsibility.

Something happens to Jonas when he gets to talk about the brownish-white birds on the cliff. His body language becomes more giddy, the gestures larger. The smile widens. That the sun shines in his eyes, he doesn’t seem to care. He has been researching the birds for almost two decades and he has no plans to leave the island.

“No, I can’t imagine why I shouldn’t be here.

Jonas Hentati Sundberg
Photo: Leif Eiranson

But it’s not just the guillemots that fascinate Jonas. He has published studies investigating Swedish commercial fishing and he is also active in the European Fisheries Inventory in the Central Arctic Ocean (EFICA), a research group that, with support from the EU, investigates fish diversity in the Arctic Ocean.

“I have a sailing drone out at sea that measures salinity, temperature and the amount of fish in the Baltic Sea. I can follow it through an app.

He shows a map on his mobile phone where he has programmed the drone to follow the flight patterns of the guillemots.

On Stora Karlsö, Jonas is busy from morning to evening. Some days, before the start of the working day, he gets up at half past five to birdwatch. Since he was six years old, he has made lists of the birds he discovers. A few weeks ago, he saw his 200th bird species on the island.

“But it wasn’t a dream species that became number 200. It was a cant tern, admittedly the world’s largest tern. I’d rather have seen something more spectacular like the 200, like kind of a spitsbergen pig.

Stora Karlsö may be the place to be

When we meet Jonas, it is still at the beginning of the season on Stora Karlsö, but it is already teeming with birdwatchers and guillemots on the island. The guillemots stand crouching over their eggs. Soon the chicks hatch and in early July the ten-day hardship begins – when the chicks jump down from the high high cliff shelf.

“The parents stop feeding the chicks a few days before they are due to leave the nest so they will be prompted to jump out, even though they are not ready to fly by then. Everything takes place at sunset, under cover of darkness. When it’s time for the chicks to leave the nest, the father leaves the shelf and lays down in the bay down here, shouting at the cub. The kid jumps out and lands down on the pebble beach, with his stomach first. Most cubs get by, because they have built up such a fat layer and have a very soft skeleton. After a minor shock, they run into the sea and find their fathers there. Then they swim off to look for food.

It’s a sight you don’t see every day, thousands of chicks jumping off the shelves, like a pouring rain of palm-sized feather balls. And a whopping 99 percent of the pig cubs survive the gigantic jump. Down on the pebble beach, the researchers, led by Jonas, meet the birds. They ring the cubs to be able to follow them for life. This year, it will be extra important for researchers to count the number of cubs, as they are simultaneously studying the sea eagles and whether the eagles’ presence still affects the population.

“My hypothesis is that the sea eagles have now realized that Stora Karlsö is the place to be and will want to be here in the future, despite the fact that there are tourists here again. We have seen some eagles circling along the cliff, but they are not as many as last year. It remains to be seen what happens, the season is not over yet.

According to Birdlife, in 2019 there were over 26,000 guillemots in Sweden, compared to 900 eagles. Wouldn’t it be appropriate to close the island to tourists to let nature take its course on Stora Karlsö – should humans really be allowed to control whether a species survives or not?

– There’s no right and wrong answer in this really, that’s what we as humans think. Either we have a view that we should do as little as possible and stay away, but I think that’s a wrong idea. Because we are already part of everything. So what we have to come up with is what we want, and how we can steer towards that.

The clock has struck five, but the sun is still shining brightly. Over our heads, swallows fly back and forth from the lighthouse, one of Stora Karlsö’s most famous landmarks. I thank Jonas for the interview. He quickly gets up from his chair. Begins to drum on the binoculars. Looking out to the horizon, he says:

– Are we done? Because then I’m leaving now. I have a lot to do. Thank you, we’ll hear from you!

Then he rushes off towards his research station.

Jonas Hentati Sundberg
Photo: Leif Eiranson
Text: Fanny Jönsson

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