Under the regular ascent and descent of Keflavík jet traffic, out past the old American radar stations, at the northwestern tip of the Reykjanes peninsula, sits the Suðurnes Science and Learning Centre. Much like the airport terminal a few kilometres from here, this spit of low-flung land is a place where many visitors to this island come and go. Along with an international team of ecologists, Sölvi Rúnar Vignisson has been working here for the past 10 years studying the oystercatcher (in Icelandic, tjaldur), a distinctive shorebird whose migratory patterns may serve as a good indicator of climate change.
Clambering into his electric SUV, we drive along the coast through the many small farms and vacation houses, on the lookout for nesting pairs. The bird is easy enough to spot. Black and white, with blood-red legs, eyes, and beak, it stands out from the muted greys and greens of the landscape. It is these distinctive features that give the oystercatcher its scientific name haematopodidae, “blood feet”.
“Now, in the lowlands of South Iceland, almost all of those individuals are migrants. Meaning they leave in the winter,” Sölvi explains. “But then you go to the western part of Iceland and you have a lot of fjords, a lot of shelter. The shores there are full of mussels and other food. These individuals are mostly residents, they don’t leave Iceland for the winter. But in this area, halfway between South Iceland and Breiðafjörður bay, we have a partial migrant population, that’s what we’re interested in here.” As he says this, Sölvi stops, quickly raising his binoculars. Clearly, he sees something I don’t, and pulling the car to the shoulder of the road, he jumps out of the car.
Oystercatchers can be found throughout the world, from North and South America to Africa, Australia, and Eurasia.
Giving chase
“The trick,” Sölvi later tells me, “is keeping your eyes on the exact spot you last saw the chick.” Bounding over uneven ground and wire fences, this is more easily said than done. At this time of year, many of them are still about as big as a tennis ball, and the moment they see us, they disappear among the many hummocks and tussocks.
We pace left and right across the field for some minutes, but this first pursuit is a wash. The young birds are too fast, and unlike their parents, their mottled plumage blends in perfectly with the landscape. “We want to look at post-fledging,” Sölvi explains. “Our hypothesis is that the mother leaves earlier. Once she sees that the chick can fly, she leaves, but the father stays and teaches the chicks to feed on their own, and ultimately teaches them whether or not to migrate. And this, we think, is why the chicks will ultimately follow the father’s strategy. Because there’s something, it could be genetic in the paternal genes, that drives the chick to migrate or not. That’s why we have to find families where both parents are ringed.”
The oystercatcher is notable for being one of the most family-oriented shorebirds. Adults will feed their young well into their adolescence, after they’ve developed their mature feathers. It’s a curious sight to see, since it looks like one adult feeding another. Oystercatchers are a very loyal bird as well, exhibiting high fidelity to both mate and nest. Indeed, this bird, which can live up to 40 years, can live its entire life with one partner at one site.
Migratory oystercatchers are also remarkably loyal to their winter destination. “The first year will hardwire them to do that for the rest of their lives,” Sölvi says. “They go to one place and then they just go directly back without stopping year after year. Maybe even to the same pier in Belfast. The wintering area is usually very small, maybe just 10×10 km, the same with their breeding area in Iceland. But the juveniles, they just go off on an adventure, following some others, and then boom! They find somewhere in Britain or Spain and think, wow, now this is nice! And then they’ll just do that for the rest of their lives.”
Our first attempt unsuccessful, we get back in the car and continue our search. Sölvi spent the first years of his research project ringing the birds of this region, and in theory, we should be able to catch and tag their young and know the migration activity of both of the parents. Lifting his binoculars up again, Sölvi sees another bird in the field. “Orange… white… NA,” he reads out. In the beginning stages of these research projects, scientists would just put different colours on the birds. Once they’d tagged quite a few, they started to run out of new combinations rather quickly. Because these birds fly all over the world, a coordinated system is needed, and now, independent non-profit organisations like EURing regulate how these birds are ringed and tracked. Now, all of them bear a combination of two coloured rings and two letters to identify them.
“What are you doing here?” Sölvi wonders aloud, binoculars trained on an oystercatcher some hundred metres away. “I remember ringing both of the individuals nesting at this site last year, but now we have an individual that’s ringed and one that isn’t.” Though known for their loyalty, oystercatchers can indeed find new partners, whether after a death, or for one reason or another choosing a new mate and relocating. This last scenario is known as true divorce. “But if I see the other individual at another site, then we know it’s a real divorce,” Sölvi says.
Once again, he takes off and runs across the field.
The Eurasian oystercatcher is the most widespread member of its family, with populations stretching from Iceland to Korea and Eastern Siberia. The West Iceland population is the northernmost year-round population in the world.
Weighing in
I assumed there might be a more scientific way of capturing the young oystercatchers than bolting madly after them. Perhaps something with an animatronic parent. At any rate, something more technical than simply running after the small birds. But at this age, they can’t fly, and chasing after them is about as good a method as any. “We’ll use traps with the adults,” Sölvi explains, half apologising. “Adults will always return to the nest, so by placing a cage and tripwire over the nest, we can use decoy eggs to lure and trap them for measurement.” Wrapped up in a wool cap in his trunk lies a clutch of clay eggs, flecked turquoise, brown, and black. “This,” he says, “is about as arts-and-crafts as it gets.”
The second pursuit is more successful than the first, and Sölvi returns holding a downy, dark brown ball. Lengths of the beak, wing, tarsus, and other biometrics are noted down easily enough. Weighing the young oystercatcher proves to be a bit trickier. For an accurate reading, the young bird needs to rest on the scale by itself, unsupported by Sölvi’s hand. Gently coaxing the juvenile, Sölvi lightly cups his hands around the bird. For a brief moment, he lets go and quickly jots down the weight.
The oystercatcher became the national bird of the Faroe Islands thanks to Nólseyjar-Páll, a sailor and poet, who was charged with illegally breaking the Danish trade monopoly. To protest the unjust monopoly, he composed a poem which cast the sheriff and other local authorities as birds of prey, and himself as an oystercatcher.
“They’re a little difficult at this age,” he remarks. “They get nervous and sometimes they shit all over you!” This explains the brown-stained bag where the young birds are kept waiting while Sölvi readies his clipboard and callipers.
After all of their information is jotted down, it’s time to tag them. Sölvi places the bird back into its waiting-bag and vigorously rubs a small piece of PVC plastic against his leg. The cold makes the plastic hard to work worth, and he doesn’t want to break it, because although it’s just a piece of plastic with some letters, they’re rather expensive when ordered in the tens of thousands. Measured and ringed, the young bird is ready to return, and either out of luck or prescience, Sölvi holds the young bird out at arms’ length, narrowly avoiding a squirt of shit.
Sölvi knows many of these birds by sight, and as we continue our cruise, binoculars at the ready, it seems to me that we’re not just in a breeding ground. We’re in a neighbourhood, each bird having lived in its nest for many years. “They’re like my friends,” Sölvi jokes. “I know them, and they are all so different. Some individuals are super chill. They’ll just go off and wait while I check their nest. Some other individuals just lose it, they go mental, fly at my head, attack me.”
Many of the birds here have already been tagged by Sölvi and he knows which nesting sites to return to year after year. Their predictability also means that Sölvi is a grandfather of sorts, having ringed and marked parents, offspring, and even generations beyond that.
Changing strategies
“The oystercatcher is important as a study species,” Sölvi explains as he drives. On continental Europe, the shorebird is one of the most-studied species of its type, but the population in Iceland still remains under-studied. With increasing changes to seasonal weather patterns due to climate change, the oystercatcher may become an important indicator of broader changes in the environment.
“We want to see how the migration strategy is changing over time,” he continues. “Historically, we’ve seen a move from along the coast towards more inland agricultural areas. And we also know that there were no oystercatchers in Iceland at the end of the last Ice Age, about 10,000 years ago. We know that the first oystercatchers must have been migrants. But then something happened. Birds began settling here, especially in West Iceland along Breiðafjörður bay. It’s much more sheltered there, and it’s warmer due to the Gulf Stream. These areas became good habitats for oystercatchers, and for some reason, they stopped migrating, or else only migrating very short distances, like from the Westfjords to the Snæfellsnes peninsula.”
Of the total oystercatcher population in Iceland, around 30% stay over the winter. “We know that because we counted them all,” Sölvi says, somewhat ruefully. “Back in 2017, we just went out in the winter and counted in the areas where we knew oystercatchers were, like in Faxaflói and Breiðafjörður. We just counted the whole lot. The estimates were around 3-4,000, but we found 11,000 individuals that wintered here.” For a population that often winter in much more southern climes, like Spain and Portugal, these 11,000 winter residents are quite the exception: “None of those populations winter at such high latitudes,” Sölvi explains. “We are way up north when it comes to wintering. It’s really unheard of for this species, but it really gives us the opportunity to look at things you can’t investigate in other European populations.”
Because the population’s circumstances are identical during the breeding season, but differ in the winter, such partial migration opens up the door for studies that can make interesting comparisons. For instance, if climate change affects winter sites differently, then the cost of migrating could become more significant over time when compared with the resident population that winters in Iceland.
Over the course of an oystercatcher egg’s development, it changes in density. Ecologists can estimate the time an egg will hatch with considerable accuracy by measuring its buoyancy in water.
The research being carried out on these oystercatchers could have wide-reaching implications. “First of all, there have not been many studies on the Icelandic oystercatcher population,” he tells me. “Secondly, most Icelandic birds are migratory and with a warming climate, it is likely that we will see more birds staying over the winter. These are changes that could have a huge impact on ecosystems in Iceland, so it is vital that we monitor and research any developments.” The main findings so far have resulted in an updated map of the distribution of oystercatchers, both in Iceland and abroad, and a better understanding of how certain nesting locations are linked to certain wintering grounds.
“The clearest example is that birds that nest in the Westfjords are much more likely to be resident over the winter, while birds in South Iceland are much more likely to be migratory,” he continues. “The distance from decent wintering grounds in Iceland seems to affect their choice to migrate or not.”
Although the oystercatcher is often loyal to its nest site and mates for its entire 40-year life, these mixed populations mean that many nesting pairs in this region of Iceland have split migratory methods, with one parent staying the winter, and one migrating. These cases of mixed parenting follow a pattern, and in every such case, the chicks will always follow the father’s strategy. For the most part, oystercatchers’ migrations are solitary. They may migrate with groups of their peers, but it’s not as if they’re making the voyage under parental supervision. This has puzzled researchers, who are still looking for answers: “How do they learn this? How is it that they always follow the father’s strategy? It may have a behavioural component, it may have a genetic component. It could also be temporal. Maybe the father leaves at a certain time, and this could influence the chick’s decision to migrate or not. There’s nothing obvious so far, but we wouldn’t be able to answer this question without the unique features of this Icelandic population.”
Bird island
With rising global temperatures, the coming decades are likely to see many changes to the migratory patterns of birds like the oystercatcher. It’s important to understand the mechanisms by which they choose whether or not to migrate. Studies such as Sölvi’s and his team’s may be laying the foundation for understanding not just how these birds migrate, but how they learn and adapt to changing environments.
Unfortunately, researchers have also begun seeing declines in oystercatcher populations. It’s too early to say for certain what the cause is, but climate change and increasingly widespread forests may be to blame.
“If we would lose the oystercatcher, that would obviously be a tragedy in its own right,” Sölvi says. “But more generally, Iceland is simply a bird island. We need these animals. You see it on Surtsey. From day zero, the day the island was formed, you can see how the birds arrived, how they started to make colonies. The first plants on the island are exactly where the birds were breeding. Now, Surtsey has many plants and insects. We have a whole habitat for other species, and it’s purely because of these seabirds. To me, it’s quite simple. If you want to protect the environment, you don’t have to control everything. You try to minimise your impact, and you just let nature do its thing.”
