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A Transatlantic Flight

Hoca

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Ospreys have been colour-ringed in the UK since the early days of the Scottish recovery in the late sixties. This has provided a wealth of valuable data on natal and breeding dispersal, longevity and, perhaps most excitingly, migratory movements. As someone who is privileged to ring Osprey chicks every year, I know what a thrill it is when a bird you have known as a nestling is seen on its wintering grounds having completed its first migration. Each winter we receive numerous reports of UK Ospreys from wintering sites in West Africa and Iberia, and as the organisation responsible for coordinating the UK colour ringing project, it is always pleasing to be able to pass these sightings onto the relevant ringer. We have received some very interesting re-sightings over the years, from a bird that returns to winter on the Canary Islands each year, to others which have migrated as far south as the Ivory Coast and Ghana. However earlier this month we received what is undoubtedly the most remarkable record of all.

A few weeks ago Michael St John got in touch with photos that he had taken on 9th March of a first-winter female Osprey with a blue-colour ring on its left leg. Nothing unusual there until I noticed where he had seen it – Bawdens Irrigation Pond in the north of Barbados in the Caribbean! The ring number was clearly visible – KW0, which indicated it was a bird from Scotland. Michael had actually first observed the bird six miles away at Fosters private wetland on 25th October 2022, but on that occasion had not been able to read the colour ring. He did, however, take some excellent photos.

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KW0 was photographed in Barbados on 9th March (photo by Michael St John)

With an increasing number of Ospreys colour-ringed in the UK each year, and an ever-growing number of Osprey ringers, it can sometimes take a while to track down who ringed a particular bird, but thanks to David Jardine and Hayley Douglas we now know that KW0 is definitely Scottish. It was one of two chicks ringed on 23rd June 2022 at a nest in Clyde Muirshiel Regional Park which lies in Renfrewshire, Inverclyde and North Ayrshire, by the Clyde Ringing Group (Iain and Madonna Livingstone, Kevin Sinclair and Paul Baker). They were assisted by staff from Clyde Muirshiel Regional Park who have supported Osprey conservation and monitoring efforts in the area, which are led by Clyde Ringing Group. Roy Dennis visited in 2010 to advise on the location of artificial nests and the first nesting attempt took place in 2017, and successfully in 2018. Last year the two chicks went on to fledge around 29th July, and likely departed on migration in late August/early September.

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KW0 was ringed by members of Clyde Ringing Group on 22rd June 2022 (photo by Clyde Ringing Group)
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The second chick in the nest, KW1, was also ringed on 23rd June (photo by Clyde Ringing Group)

As far as we are aware, this is the first time that a UK Osprey has been observed in the Americas. It is 4124 miles from Clyde Muirshiel to Barbados. This is the kind of distance that many Ospreys from northern Europe will migrate each year – some Finish Ospreys are known to winter in South Africa, which is considerably further – but of course what makes this record amazing is the fact that the vast majority of the journey is across the Atlantic Ocean. We know from satellite tracking studies that Ospreys are able to make much longer sea crossings than most other raptors. Their long narrow wings reduce drag and make active flapping flight, which is usually necessary over the open ocean, less energetically costly compared to larger, heavier species. Juvenile Ospreys, which migrate alone, and rely on a process known as vector summation (an inherited programme of distance and direction) to migrate to distant wintering grounds, are particularly likely to make long ocean crossings because, unlike adult Ospreys, they are usually unable to correct for displacement by crosswinds. In other words, if a juvenile Osprey, which is instinctively migrating south-west, encounters strong easterly winds it will drift further to the south-west. This coupled with the UK’s position on the edge of Western Europe means that juvenile Ospreys often fly direct across the Bay of Biscay from southern Ireland or South-West England to northern Spain during their first autumn migration. Others also make long flights from South-West Portugal to North-West Africa. In one exceptional case a juvenile male Osprey, known as Stan, which was satellite-tagged by Roy Dennis in northern Scotland in 2012, completed an amazing eight-day migration to the Cape Verde Islands, situated in the Atlantic, approximately 400 miles off the West Africa coast. Stan’s flight included a 620 mile crossing from Portugal to Lanzarote in the Canary Islands, and then a non-stop 930 mile flight to the island of São Nicolau in Cape Verde. Unfortunately, Stan’s transmitter stopped working eight days later, and we speculated at the time that this may have been due to the fact that he tried to continue on the same south-westerly course and then drowned at sea.

Even Stan’s remarkable migration pales into insignificance compared to that of KW0 who is likely to have flown 3800 miles (6114km) across the Atlantic from South-West Ireland to Barbados. It is highly unlikely that even an Osprey could have completed this in a single flight, even with strong tailwinds, and so it is probable that she took the opportunity to rest on boats, which may themselves have been travelling to the Caribbean from the UK. Other satellite-tagged Ospreys are known to have interrupted their journey in this way in the past. In fact, a satellite-tagged juvenile known as Chip almost made it to the Azores from New Hampshire in this way. It could be that KW0 stopped-off on the Azores en route to Barbados. One thing we can be certain of is that KW0 must have departed on migration in exceptional condition in order to have survived this remarkable transatlantic crossing.

Having spent at least four-and-a-half months in Barbados, KW0 is clearly very settled at present, and, in fact, may well remain there for the foreseeable future. Young Ospreys usually remain on the wintering grounds for the whole of their second calendar year, meaning that KW0 could linger in Barbados until spring 2024. Quite what happens then remains to be seen. Most Ospreys fly north back towards their natal area during their third calendar year, but clearly that is unlikely to be an option for KW0, who may instead choose to remain on the other side of the Atlantic. Let’s hope we receive further sightings of this remarkable young Osprey in the months ahead.

Tim Mackrill, 24th March 2023

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KW0 (above and below) was first observed in Barbados on 22nd October 2022 (all photos by Michael St John)
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