Scientists at the University of East Anglia (UEA) are tracking white storks ina bid to find out about migratory habits that disappeared more than 600 yearsago.
It follows the release last month of 19 captive-bred young storks at KneppEstate, West Sussex, as part of the White Stork Project, which aims toreintroduce them as a breeding bird in the UK. The project is led by apioneering partnership of private landowners and nature conservationorganisations.
The birds joined another four juvenile storks that fledged from two nests inthe wild at Knepp this year – the first successful nests in Britain since the15th century. Migratory birds, white storks used to be native to Britain, butthe last pair recorded nested on the roof of St Giles Cathedral in Edinburghin 1416.
For a trial in 2019, the research team at UEA and the Durrell WildlifeConservation Trust fitted GPS trackers to eight storks, which were thenreleased. The devices have been developed by Movetech Telemetry – apartnership between UEA, the British Trust for Ornithology and University ofPorto, Portugal – and this year they were fitted to another eight youngstorks.
These birds are providing data that will enable the researchers to gaininsights into the life and migratory choices of the reintroduced storks. Acharismatic species that is happy to live alongside humans, they feed onagricultural land and nest in trees but also on chimneys and power lines. Infolklore, they have been associated with the arrival of babies.
Dr Aldina Franco, associate professor in ecology at UEA, leads a researchgroup investigating changes in the migratory behaviour of birds. She said:“The reintroduction of storks in Britain will have both ecological andcultural value and having this species restored to the UK landscape will be afantastic achievement.
“In Britain there are no experienced migratory birds so the reintroducedbirds, those migrating will have to find their migratory way and return in thespring.”
European storks migrate to Southern Europe and Africa in the autumn and havetwo main routes – the eastern and western migratory routes – with a migratorydivide in Germany.
Dr Franco added: “In the past, British storks probably used the westernmigratory route but storks from Poland use the eastern migratory way. InSouthern Europe some populations are no longer migratory and spend the wholeyear near the breeding area.”
Previously unpublished data from the 2019 trial reveals that many of thestorks spent the winter at landfill sites in Southern Europe and NorthernAfrica, where they have adapted to take advantage of new food resources andgather in large numbers.
Initial data from the birds released this year indicates that migratory storkscrossed to Continental Europe via Dover-Calais. Three storks are now in Spainusing landfill sites, two are in France and one is still in the UK. One storkdied in the UK and one in France is no longer transmitting, which the teamis investigating using local contacts.
“There is a high level of excitement and anticipation after deploying thetracking devices, as we don’t know what the birds will do or if they willsurvive the migration,” said Dr Franco.
“In 2019 some of my colleagues were positive the UK storks would remain in thecountry, others thought they would migrate using the western migratory route,while I thought they follow their parents’ route towards the East. In fact, wewere all right, and astonished to see the diversity of strategies individualsadopted.
“The 2020 storks will encounter other individuals and follow leader birds –older animals that are more experienced – in migration. They may spend winterin a range of locations depending on the storks they encounter on the way.”
The tracking devices have the potential to track the storks for several years.‘Marge’, one of the best known storks from the 2019 release, is stilltransmitting. She spent the first winter near Rabat, Morocco, and returned toMorocco recently after a summer trip to Donana, in Southern Spain. Some of the2019 birds remained resident in Britain.
Lucy Groves, White Stork Project Officer for the Durrell Wildlife ConservationTrust, said they are already seeing the results of changes made since lastyear to improve the tracking.
“Storks helped to unlock our understanding of bird migration when in 1822 astork appeared in Germany with an African spear through its neck, proving thelong journey they take each spring and autumn,” she said. “Today, we havetechnology to give us detailed insights. Lightweight GPS tracking devicesenable us to increase our understanding and knowledge of these birds’incredible journeys.
“There have been many suggestions put forward as to what our British storkswould do. Would they stay here over winter? Would they migrate? Which routewould they take if they left our shores?”
She added: “It has been fascinating to follow the individual migration routestaken since August 2019 and the data collected is allowing us to build up apicture of the wide range of behaviours and patterns displayed by ourjuveniles.
“It was amazing to watch Marge, who left the UK just two days after beingreleased and, although she headed east to start with, she then continued onher journey south west and became our first British white stork to cross thestrait of Gibraltar into Morocco. A huge success for the project.
“The combination of sightings and GPS data has shown that these juveniles areintegrating with wild populations of storks, following the more experiencedbirds once they meet them in Europe. I am looking forward to seeing if our2020 juveniles pick the same or different routes and if any will join Marge inMorocco?”
The juvenile storks released this year were offspring of captive-bredparents at Cotswold Wildlife Park, which are injured or incapacitated storksrehabilitated and donated by Warsaw Zoo.
Similar reintroduction schemes, aiming to boost white stork numbers acrossEurope, have been implemented in the Netherlands, Belgium, Switzerland andSweden.
Image Credit: Kevin Harwood
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