Effective method endangered ospreys are making a comeback

By Stephen Beech

Ospreys are recovering in Britain thanks to "pioneering pairs" who prefer to nest away from the main population, reveals new research.

They could be key to increasing the spread of the raptors who became extinct in the British Isles in 1916 before recolonizing in 1954, say conservationists.

Researchers looked at a rare long-term dataset covering 54 years of recolonization of ospreys in northern Scotland.

They investigated the distribution and density of nests and the resulting patterns of settlement to understand how ospreys spread and what drives spatial recovery.

The study, published in the Journal of Animal Ecology, was led by Bournemouth University Ph.D. researcher Brittany Maxted working with the charity Birds of Poole Harbour, and The Roy Dennis Wildlife Foundation which monitor ospreys in parts of northern Scotland.

Maxted said: "Ospreys usually like to nest in areas where there are already other ospreys, which we refer to as conspecific attraction.

"Most males also exhibit natal philopatry, which means they tend to breed close to their own birthplace.

"Together, these factors lead to very slow population spread for such a large bird.

"However, in Scotland we noticed that a small number of pairs were choosing to settle more than 20 kilometers away from all the others, in areas with no competition.

"We call these 'pioneering pairs' as they recolonize new areas, and in doing so create separate subpopulations and increase the speed of recovery for the species."

Restoring lost species is a key goal for conservationists, but very little is known about the process of recolonization.

The research team found that the patterns seen in ospreys are very similar to other types of population expansion which have been much better studied, such as invasive species.

Study co-author Tim Mackrill, lead ornithologist at the Roy Dennis Wildlife Foundation, said: "This study highlights how much the spatial expansion of ospreys relies on the long-distance dispersal of these rare pioneering individuals.

"It suggests that the best way to accelerate natural recovery rates is for conservationists to encourage or even replicate these pioneering movements.

"We can do this by building artificial nests to help entice ospreys into new areas or by physically moving individuals via translocation."

Ospreys once bred across much of Britain, but by 1916 they had disappeared as a result of hunting and egg collecting.

But after a pair naturally returned to a nest site at Loch Garten in Scotland in 1954, a conservation movement began to protect nesting pairs and help the species recover.

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Roy Dennis has been monitoring and conserving the Scottish population since the 1960s, leading to the dataset used in the new study.

He said: "It's fantastic that this dataset, which we've collected over many decades, continues to teach us more about these remarkable birds.

"Our findings reinforce that we're taking the right approach to restore ospreys across the U.K. and beyond, and suggest that we should be using these measures even more widely to see faster recovery of the species across Europe."

One example of where the techniques have already helped ospreys recover is in Poole Harbour, Dorset.

Starting in 2017, the Roy Dennis Wildlife Foundation and Birds of Poole Harbour ran a five-year translocation project, moving young ospreys from northern Scotland to Poole Harbour.

Healthy chicks were taken from longstanding nests at 7 weeks old and moved temporarily to hacking cages in Dorset to finish developing before being released into the surrounding landscape, which they quickly came to recognize as home.

Maxted said: "Through translocation we can essentially create our own pioneering birds to kickstart a new population.

"The first breeding pair in Poole Harbour was a male named 022 who we had translocated from Scotland, and a female named CJ7 who had visited from a population 200 kilometers away and was attracted to stay by the presence of translocated chicks.

"In 2022 they hatched two chicks of their own, becoming the first breeding ospreys in southern England since 1847.

"If it wasn't for the translocation project, we may have had to wait another 60 years for breeding ospreys to reach Dorset naturally."

Conservationists have described it as a "huge success story" with the original Poole Harbour pair returning to breed and producing chicks at the same nest each year since.

This summer they have hatched four chicks for the third year in a row, all of which will remain in the area and reliant on their parents for food until they leave on migration around early September.

And several pioneering movements have also been recorded, with a second pair breeding away from the harbour and the first wild born Poole Harbour chick now breeding in the East Midlands.

Both pairs are forming new subpopulations and starting to close the gap between Poole Harbour and the nearest osprey population in Rutland Water.

Maxted said: "Translocation is an incredible tool, but it can take many years to see the results.

"We're still in the early stages in Dorset, but are already seeing some of the first wild born chicks returning, with four eligible young males currently exploring suitable nest sites and looking for mates."

She added: "We hope that in the coming years some of them will become pioneers themselves, helping the population spread along the south coast of England.

"Artificial nests have already been built for them in neighboring counties like Devon and Hampshire, and based on the results of our study we'll be aiming to provide lots more."

The team hopes their research will motivate more conservation action for ospreys across Europe, where they are still missing from much of their historical range.