Following two weeks spent acclimatising in a special enclosure near Vylkove, a town on the edge of the Ukrainian part of the Danube Delta, it was time for four young eagle owls to leave.
Though the birds were inquisitive about the open door, it was only when the aviary’s roof was carefully rolled back by members of the team from Rewilding Ukraine that they began to make their move.
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They jumped up to perch on the shelter’s perimeter, their huge golden eyes surveying their new surroundings. Then, after just a few minutes, wanderlust got the better of the first owl, which opened its huge wings and soared into the nearest tree.
It was met by a cacophony of cawing from the confused corvids already among the branches, unsure of what to make of this huge intruder.
Within an hour the four owls had joined 15 others previously reintroduced into Europe’s largest remaining wetland. The programme began with one ‘pioneer owl’ in 2019, and has been followed by four further releases over the past six years.
Rewilding the Danube Delta
Four weeks earlier, I had been speeding east from the town of Tulcea along waterways on the Romanian side, accompanied by Ioana-Catalina Petrencu, who heads up the Danube Delta team at Rewilding Romania.
The ongoing conflict meant it was impossible to meet up with their Rewilding Ukraine colleagues, but there had been sightings of an eagle owl at Ultima Frontiera, a lodge close to the Ukrainian border.
This was our destination and, as well as searching for an elusive owl, the team planned to carry out land assessments and monitor waterbirds, particularly the Dalmatian pelican.
The delta is a vast mosaic of rivers, lakes and marshes, where freshwater mixes with tides from the Black Sea to create brackish lagoons.
There are huge areas of grassland, steppe and forest, too, as well as shifting sand dunes that are continually on the move – an old lighthouse at Sulina is now 6km from the coast.
I spot herons, egrets and kingfishers patrolling the waterways, while white-tailed eagles stand sentinel on treetops and electricity pylons. Black storks circle high on the thermals and squadrons of pelicans form dark V shapes as they flap lugubriously across the delta’s big skies.
The occasional golden jackal appears on the riverbank, watching quizzically as we edge past.
Small fishing boats drift along, rods dipping into the water in search of carp, one of more than 60 types of fish – including four species of sturgeon – that make the delta home to the largest diversity of fish in Europe.
Side channels lead us away from the main waterway into lakes where pelicans and pygmy cormorants perch on slowly decaying tree stumps, while hundreds of swallows skim the surface, skipping up with beakfuls of midges.
Some of the lakes are covered in the triangular leaves of water chestnut, a food staple for people that still live on the delta. Others are swathed in water lilies, which provide convenient nesting platforms for coots and terns in the spring.
Finally the delta throws us out into the Danube proper. Ukraine faces us on the far side and, soberingly, we pass a partially submerged gunboat, hit and sunk by a drone.
“It’s still a very wild place,” says Petrencu, over the whirr of the outboard motor. “The ecosystem is pretty complete and there is still a lot of diversity.”
“Rewilding is based on letting nature lead,” she continues. “It’s about not intervening unless something is missing.”
In the delta, the eagle owl is one of those missing species, and in Ukraine it is being reintroduced with a very specific role – to control the spiralling population of rats that threaten the eggs and chicks of ground-nesting birds such as plovers and avocets.
The restoration of the delta, including the breeding and release of eagle owls, is being funded by a $2.4m grant from the Endangered Landscapes & Seascapes (ELSP) initiative. The six-year project is one of more than 20 across Europe helping to restore ecological processes and reintroduce species.
The latest releases into the delta – two males and two females – were born at Limpopo Zoo, near Lviv.
After hatching, the birds matured in conditions that were as close to the natural world as possible, before being moved to Odesa Zoo, where they learned to fly and hunt. Their final two weeks of captivity were spent getting used to the smells and sounds of the wild.
The process is called hacking, explains Mykhailo Nesterenko, a Rewilding Ukraine team leader, and it’s a common way to prepare birds of prey for release.
“You want animals to believe they were born here,” he says.
At least two owls from each release have been fitted with transmitters, which have shown that, while some owls have explored the wider Danube region, they eventually return to the Ukranian side of the delta.
Return of an apex predator
The eurasian eagle owl (Bubo bubo) is the largest in Europe, standing 75cm tall with a wingspan of up to 180cm. With prominent ear tufts known as plumicorns and a booming call, it is an apex predator with a real taste for rodents.
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Once widespread across Ukraine, the owl is now restricted to a couple of regions in the north and east of the country.
“Like all birds of prey, eagle owls were persecuted in the past,” says Nesterenko. An eradication programme ended in 1969, marking a turning point in the species’ legal protection. Hunting is now totally banned.
Collisions with powerlines have also taken their toll, but have been significantly reduced by installing bird diverters that make the cables more visible. The use of poisons to kill rats, which the owls feed on, has also been restricted.
The definitive book on the species, simply called The Eagle Owl, was written by Vincenzo Penteriani and María del Mar Delgado.
Delgado explains how eagle owls lack an adventurous streak and, once they fledge, “They don’t disperse, they don’t explore.”
As a result, nature can’t be relied on to repopulate an area, so human intervention is needed. But reintroductions need to be carefully managed: “Eagle owls can prey on almost anything… they are super-predators.”
A penchant for domestic cats was one of the reasons eagle owls were persecuted on the delta, and the predators have also been known to take much bigger birds, such as herons, while the remains of peregrine falcons have also been found in their nests.
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But these events are rare, says Delgado, and happen only when there’s no other prey.
Eagle owls are crepuscular and hunt when the light begins to fade, patrolling three or four areas close to their roosting site. Their diet is eclectic – ranging from hedgehogs and amphibians to large insects – and the birds are equally unfussy about where they nest.
Often, they take over the nests of other birds, such as storks, buzzards and eagles, and while they prefer a lofty cliff or quarry, they will also nest among stones on the ground, and even in the roots of upturned trees.
Unlike many owls, they shun tree-holes. “They’re very big and need to jump from the nest to start flying,” says Delgado.
Restoring the delta
The eagle owl reintroduction is just one of the efforts to restore and rewild these wetlands. The delta has been developing for thousands of years, after the Danube broke through into the Black Sea, turning flooded river mouths into huge lakes such as Kartal and Yalpuh.
Ever since, people have been tampering with this landscape’s flow of water.
Perhaps the most drastic changes came after World War II, explains Nesterenko, as people faced famine, food shortages and a new era of communist rule.
Huge areas of the delta fell under the plough, while dykes, drains and polders channelled water to fish farms and irrigation schemes. These efforts to tame the river led to a drop in water quality, salinisation and loss of biodiversity.
Throughout the communist era there was a constant push for development, explains Petrencu. In the 1990s, conservation was mentioned for the first time.
“People said things about destruction, but they were silenced,” she explains. “Now we are feeling the effects of what happened in the past.”
With the break-up of the Soviet Union, there was more change. Inefficient industries collapsed as government subsidies disappeared, and agriculture fell into decline.
The land was no longer managed, allowing the common reed to grab a foothold. The delta offered the perfect conditions for this thuggish plant to flourish, as it colonised meadows and the verges of abandoned fields, slowing the natural flow of water.
The dried reeds also provide tinder for wildfires.
Large herbivores have a crucial role to play in combating the explosion of reeds, and several species have been reintroduced to Ermakov Island, part of the Ukrainian delta, with the support of ELSP.
These include kulan, a wild ass extinct in Europe for more than 200 years; Konik horses; and both red and fallow deer, all of which have a taste for the reeds’ young shoots.
But the real stars are water buffalo, true landscape architects that trample the reeds as they eat, creating new clearings and pools. The animals in the area today are related to 15 that were released in 2019, but the history of water buffalo here stretches back to the days when it was part of the Ottoman Empire.
Rewilding work also involves reopening channels and waterways, and removing human-made controls, such as obsolete dams and dykes, to restore natural floods and flows.
Some of the communities that live on the delta are among the remotest in Europe, and it is important that the rewilding benefits them, too, says Nesterenko.
“We are restoring natural connectivity and the natural dynamics of the delta,” he says. This helps prevent flooding, as well as opening up spawning grounds for fish and improving water quality. Ecotourism is also providing new opportunities.
“It’s a beautiful dream to turn the delta back into a wetland,” adds Petrencu. “Our goal is not to put a fence around everything. People need to benefit from nature in a responsible way.”
Despite our best efforts, we don’t see or hear an eagle owl at the lodge. But one night I am awoken by a distant rumble, and in the morning look across the Danube to see smoke rising from Vylkove.
It is difficult to reconcile how so much time and attention has been lavished on four owls by a country that had been at war for nearly four years.
Yet nature has always played a central role in Ukrainian life. Even amid the chaos of war, the country plans to create two new national parks.
Further annual releases of owls are planned as part of the long-term reintroduction programme.
Nesterenko’s dream is to find evidence that the owls are breeding, which will confirm that this apex predator really has returned, and that its deep, resonant hoot will once again be a common sound echoing across the delta.
Mark Hillsdon travelled to the Danube Delta courtesy of Endangered Landscapes & Seascapes.
Top image: a Eurasian eagle-owl flying through a forest in Czech Republic. Credit: Jan Drahokoupil/Getty Images
