Meet the Baltic Dunlin
The dunlin is a shorebird that is widespread across the northern hemisphere. You can see them from Alaska in the far west to Kamchatka in the far east. Across this range, there are several subspecies,* and the Baltic dunlin belongs to the schinzii subspecies, which breeds in Greenland, Scotland, the North Sea, and the coastal meadows around the Baltic Sea. The Baltic dunlin is perhaps the most endangered shorebird population in Europe. The Finnish population has declined from around 200 pairs at its peak in the 1960s to fewer than 50 pairs today, most of which breed in the Bothnian Bay. As a result, the Baltic population is listed as an Annex I species in the European Birds Directive, highlighting the critical need for appropriate conservation measures. To halt the steep decline, researchers experimented this year—for the first time—with headstarting as a method to boost the population. More on that later!
So, how can one recognize the schinzii subspecies? Compared to the alpina subspecies — which is rather common in the (sub-)Arctic — schinzii birds are a bit smaller, have a shorter bill, and, most importantly, have duller-colored summer plumage and often lack the nice black belly, instead their belly is a mixture of black and white. Differentiating between the subspecies in their winter plumage is nearly impossible. The Baltic dunlin visits the Bothnian coastal meadows from May to July before returning to its wintering grounds in North Africa, with Banc d’Arguin in Mauritania as a prime destination. During migration, they spend considerable time in the Wadden Sea, where they feed heavily before embarking on the long journey to Africa.
Let us now delve into the research being carried out in Oulu to find out why the life of the southern dunlin is so precarious.
* Subspecies: A subspecies is a group of individuals within a species that are highly genetically and often morphologically differentiated. However, subspecies can still interbreed. Two species that successfully interbreed almost always produce offspring with highly reduced survival.
This photo shows a dunlin ssp alpina. Note the ruddy back and black belly.
This photo shows a dunlin ssp. schinzii. Do you see the difference? Yes, there is no nice black belly.
On the highway towards extinction?
Kari Koivula and Veli-Matti Pakkanen have been studying dunlins in the Bay of Bothnia for over twenty years. During that time, they have witnessed the species’ decline firsthand.
Each year, researchers from the University of Oulu collect population data. The field season begins in May, when the first male dunlins arrive. Upon reaching the breeding grounds, the males immediately start searching for suitable territories, preferring areas with short grass. Male dunlins often return to the same territory for several years. They are also largely monogamous and will wait for the female they mated with the previous year. Cute, isn’t it?
Displaying males are relatively easy to spot thanks to their characteristic “prrrrrrrtttttt” call. Once a male successfully attracts a female, he prepares several nest scrapes in the grass for her to choose from.
Then the real challenge for researchers begins: finding the nests! The eggs are tiny and perfectly camouflaged by their color. Even with the GPS coordinates of the nest site, additional landmarks are often needed to locate it - the nest hole can easily disappear in the tangle of grass.
Searching nests is pretty straightforward. You just walk and walk until you flush a bird from the nest. Then you try to spot the eggs, which can be very tricky.
After the eggs hatch, both the chicks and their parents are fitted with metal rings. Adult birds also receive an additional color-ring code so they can be easily identified later in the field. The researchers take blood samples as well which is crucial for genetic analyses. For example to quantify inbreeding or determining relationships.
In 2025, there was a major push for headstarting, which I’ll tell you more about later. But here’s a sneak peek: the eggs are collected and hatched at the university facilities in Oulu. Every now and then, though, a pair escapes our notice, leading to scenes that are both cute and bittersweet. Because despite all our efforts, one question keeps lingering: will these conservation measures come in time to prevent something worse?
Jelena opens a bag of hand warmers to keep the chicks warm while ringing.
A 1-day-old chick receives it metal ring;
1-day-old dunlin chicks, they are cute, aren't they?
Is there still hope?
There are several reasons behind the dunlin’s decline in this area. To uncover them, we first need to take a closer look at their breeding habitat.
The coastal meadows we see today are not pristine nature. They have been largely shaped by humans. Originally, dunlins occurred in small numbers in open, sparsely vegetated areas created by land uplifting*. People also discovered these areas for grazing livestock. This grazing ensured that coastal grasslands remained open and prevented further succession to reeds or forests. After the 1960s, this traditional management disappeared, and many meadows became overgrown. In recent years, efforts have begun to restore these grasslands through grazing. At first glance, this seems like a solution to the overgrowth, but restoring coastal grasslands and their associated biodiversity is not so simple.
Too low grazing pressure has little effect, so the succession continues. Too high grazing pressure can lead to too many nests being trampled. A possible alternative is mowing at the end of summer, when the chicks have already fledged. Nature management remains complex. Due to higher nitrogen deposition and more nutrient-rich water from the Bay of Bothnia, grass and reeds are growing faster than ever.
Moreover, coastal grasslands are regularly flooded by strong southwesterly winds, which push water from the Baltic Sea into the bay. Due to climate change, such flooding is occurring more frequently and earlier in the season—precisely when the dunlins are breeding or have chicks. Such events can have disastrous consequences for the population.
Habitat loss and flood risk are closely linked. The higher parts of the meadows become overgrown, forcing the dunlins to breed closer to the coast, where the grass is shorter, but the risk of flooding is greater. In other words, they are caught between a solution and a new problem.
*A large pack of ice pressed on the Fennoscandian land during the last ice-age. Since the ice and associated pressure on the land has disappeared, land is lifting upwards. Because of this, countless small islands emerge in front of the Swedish and Finnish coast.
Summer flooding in the meadow
In addition, habitat change also creates a significant secondary problem: predation! Living in coastal grasslands is not without risk. A wide range of deer-eaters benefit from the abundant food resources available here. Harriers, kestrels, peregrine falcons, and foxes frequent the grasslands. They are all hungry and searching for food. In years when voles and other rodents are abundant in the inland forests and fields, hunting pressure on birds in the coastal grasslands is lower. Unfortunately, the vole cycle is no longer as predictable as it once was, and predators are likely to target birds in the coastal grasslands than they were in the past.
Small populations also fall victim to inbreeding. This means that closely related individuals breed with each other, which negatively impacts the survival of the native species, putting the population at even greater risk of extinction. This became clear when we found a nest in 2025 that failed to hatch. The parents were incubating. The eggs were infertile. When you shine a bright light through the eggs, you can -normally- see the embryo (called candling).
Because problems accumulate in small populations, ecologists found a special term for this negative spiral: the extinction vortex.
There are not many options left to save a small, endangered population like the Baltic dunlin. One of the last resorts the Oulu research group is starting to explore is a head start.
A cute video to cheer up this potentially depressing blog. Here you can see the adult male starting to brood on the chicks again after ringing. The males are mainly responsible for raising the chicks.
Headstarting as a last resort?
Headstarting is a conservation method that has gained popularity in recent years. In short, these projects boost populations of endangered species by bridging the most critical phase of their life cycle in captivity.
For birds, the first step in a headstarting project is to collect eggs in the field. Sometimes, dummy eggs are placed in the nest to prevent the parent birds from leaving. When the eggs hatch in captivity, the chicks can occasionally be re-adopted by their parents.
We chose not to place dummy eggs in the nest cups. The reasoning is that when eggs are collected early in the season, the pair can still produce a replacement clutch—potentially increasing the number of offspring (hooray!). Unfortunately, we found few replacement clutches. This may be explained by flooding in June, which likely caused some of these second attempts to fail.
Once at the university, the eggs are hatched in incubators and carefully monitored. In 2025, Veronika Rohr-Bender took on this task. Under her expert care, all 26 fertilized eggs hatched; two were unfertilized.
Eggs of three dunlin clutches in the incubator of the Oulu University. It takes about 22 days for dunlin eggs to hatch.
The real work begins now: ensuring the chicks grow well. Fortunately, wader chicks are easygoing. In the wild, they immediately begin foraging on little insects once they are out of the eggs. In captivity, however, they have to rely mainly on specialized breeding food.
Fortunately, a fresh batch of mosquito larvae arrived every so often—which the chicks absolutely loved! The biggest job was keeping the breeding boxes clean, because those chicks can poop a lot!
The baby's!
Hmmmm! Mosquito larvae!
Finally, when they are big enough, the chicks go to the aviary to acclimate to outdoor life and continue growing. It's amazing how fast they grow! In addition to their pelleted food, the chicks also received small crickets to help them get used to live food. Sometimes we even release some insects we caught ourselves into the aviary.
But soon it started to wander around!
They grow so fast! During some days they could earn up to three grams body mass!
Check my wings!
Hmmmm, tasty cricket!
I also spied on the chicks with a GoPro camera. This cube is full of magic and provides so much adorable footage. In 2024, I was able to film the first time they tried to fly, the first time a bird tried to catch a fly, and when they took a bath. By closely observing the chicks, we noticed that each bird had its own personality. Yellow was the most daring and not at all shy about posing for the camera. Red and Green spent most of their time sheltered under the box. Yellow was also the bird that grew the most. Yellow is probably a female, as females are generally larger than males. After about ten days, the daily feeding routine became more challenging as the birds started flying around in the cage. This was the sign that it was time to release the chicks into the wild. In general, the chicks were then about a month old.
GoPro video showing the first attempt of Yellow to catch an insect!
When the chicks are old enough, we release them. The most important thing is that they can flyn to escape predators. We released the birds in various coastal grasslands where they naturally occur, preferably near gull or tern colonies. These birds are quite aggressive toward predators and thus act as our chicks' bodyguards. Ruff and redshank broods also often forage near such colonies to benefit from the free bodyguard services.
Although I was happy to see the dunlins roaming freely, I was moved to tears. I hope they survive all the dangers in the big, wide, wild world. Meanwhile, hopefully, they have arrived at their wintering grounds in Africa, where they will spend almost two years, although females often return after just one year. I will be so happy when they are reported back to Finland!
And there they go, hopefully ready for the big wild world full of danger.
Hopefully, this headstarting project will get the Baltic Dunlin population away from the highway to extinction. Anyway, these dunlins have won a special place in my heart, and maybe in yours too?
Written with much appreciated thanks to the feedback from Jelena Belojevic!
More information:
- About Baltic dunlin migration: A paper by Veli-Matti Pakanen and others titled "Migration strategies of the Baltic dunlin: rapid jump migration in the autumn but slower skipping type spring migration"
- About the flooding problem: A pre-print paper by Kari Koivula and others titled "Increased Wind Flood Frequency Leads to Decreased Nest Success of Endangered Waders in Managed Shore Meadows"
- About the inbreeding problem and extinction vortex: A paper by Donald Blomqvist and others titled "Trapped in the extinction vortex? Strong genetic effects in a declining vertebrate population" on the Swedish Baltic dunlin population
- About the habitat changes in the Botnian bay and a broader genetic context: A paper by Nelli Rönkä and others titled "Genetic differentiation in an endangered and strongly philopatric, migrant shorebird"
- About the disturbed vole cycle and its influence: A paper by Veli-Matti Pakanen and others titled "The abundance of small mammals is positively linked to survival from nest depredation but negatively linked to local recruitment of a ground nesting precocial bird"
- About the Swedish Baltic dunlin conservation project: https://en.nordensark.se/nyhetsarkiv/head-start-for-southern-dunlins/
- About a British headstart project focussing on godwits: https://www.waderquest.net/conservation/headstarting/