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The explorer returns

Hoca

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During the course of the first four years of the Isle of Wight White-tailed Eagle project, which we run in partnership with Forestry England, the young eagles have followed a fairly predictable pattern. They disperse widely during their early years, but then move back towards the Isle of Wight and the South Coast as they approach breeding age. This is demonstrated by the fact that the first two territorial pairs have become established on the Isle of Wight and in the Arun valley in West Sussex, despite the fact that three of the four birds involved spent time in Scotland during their second calendar year.

The latest bird to return to the Isle of Wight after a prolonged period away is 2020 male, G463. He was the first Isle of Wight bird to cross the English Channel and spent seven months in Continental Europe between April and November of his second calendar year, favouring the Wadden Sea coasts of Netherlands, Germany and Denmark. When he returned he spent the majority of the winter in East Anglia, mainly in north and west Norfolk, but also visiting the Suffolk coast. Later he also re-visited a favoured area near Chard in south Somerset, where he had spent his first winter, but made no attempt to return to the Isle of Wight.

On 3rd April last year he made a second crossing of the Channel, and returned to many of the locations he had visited the previous summer, and also made a short excursion into Sweden. It was notable that like many of the other young eagles, he was returning to favoured locations first encountered during his initial explorations.

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G463’s movements from 13th October 2020-31st December 2021 (red) and 1st January 2022-9th January 2023 (white)

One of the places G463 re-visited during his second visit to mainland Europe, was the Biesbosch, a large wetland in the Netherlands which supports breeding White-tailed Eagle and Osprey. Whilst G463 was there we received images taken by a local photographer, kindly sent to us by Dirk van Straalen who monitors White-tailed Eagles in the Netherlands. We were very concerned that the photos clearly showed the bird was missing his right leg below the knee. We initially suspected that this was a recent injury, but when we analysed the satellite data it was clear that G463 had been behaving apparently normally for several months; indicating it probably occurred earlier.

The tag’s in-built accelerometer, which provides data on the eagle’s movement, indicates that G463 probably sustained the injury in December 2021 when he was in North Norfolk. White-tailed Eagles favour the sit-and-wait strategy when searching for food, and consequently are are often static for prolonged periods. However, in this case, the data indicated G463 was more sedentary than usual, and so the Foundation’s Associate Ornithologist, Zoe Smith, a highly experienced raptor fieldworker, made a specific visit to try and locate him. The eagles can be very difficult to track down depending on their location, but with the permission of the landowner, Zoe was able to locate G463 perched inconspicuously, and not easily viewed, in a quiet area of woodland. A few days later we were encouraged that he became more mobile again.

In January G463 moved further south and was seen and photographed at various locations in Suffolk, including at RSPB Minsmere at the end of the month. Close inspection of photos taken at the time indicate that the right foot was missing, even though it again went unnoticed. This supports our hypothesis that G463’s period of inactivity the previous month was due to the injury.

Having sought advice from the project’s vet and raptor expert, John Chitty, it seems that the injury could have been sustained in one of two ways. The first is through loss of blood due to entrapment or entanglement, and the second is through electric-shock, which is known to cause raptors to loose legs in the manner of G463 (see here for some examples).

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G463 at Minsmere on 31st Januay 2022 (photo by Rachel Harvey)

Regardless of the exact cause, it appears that G463 has learnt to adapt to living with only one foot. He returned across the English Channel on 20th September 2022 and initially returned to favoured areas in West Norfolk, where he remained until the end of October. He then made his way slowly south-west to Somerset and spent six weeks in south Somerset, before heading east to Poole Harbour on Boxing Day. Finally, on 9thJanuary he returned to the Isle of Wight for the first time since 13th October 2020. During his 27-month period away – the longest of any of the released eagles so far – he flew over 17,000km and visited seven different countries.

On his first night back on the Isle of Wight, G463 roosted close to the release area, but like other returning eagles, he had the Island’s resident birds, G274 and G324 to contend with. The satellite data showed they roosted very close to each other that night, and then G463 remained in the local area for most of the next day. However, on the morning of 11th, the tracking data indicates that G463 was seen off by G274 and, after spending two further nights on the Isle of Wight, albeit in areas away from the resident male’s core territory, G463 headed back across the Solent during the afternoon of 13th. He flew north across the New Forest and spent several days near Amesbury in Wiltshire, before heading south-west and returning to Poole Harbour.

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G463 at Chard Junction Gravel Pits on 27th November 2022 (photo by Dave Helliar)

Poole Harbour has become something of an eagle hotspot over the past twelve months and on the morning of 21st January G463 was photographed by John Thorpe, Pete Scott having an aerial tussle younger male G812, who has been a regular visitor to Poole Harbour in recent months. He then spent the rest of the day with 2020 female G466, who returned to the South Coast in early October after spending last summer in northern Scotland, and has been another regular in the area. With both birds now in their fourth calendar year they are reaching the age where we might expect them to pair up and establish a territory, and so it be interesting to see what happens over the coming weeks. We will be paying particular attention to G463 to understand better how he has adapted to living with only one foot. Birds can be remarkably adaptable and there are examples of Bald Eales living with only one foot in North America (see here). The fact that G463 has survived for more than a year, is certainly encouraging. We will be sure to keep you updated over the coming months.

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G463 (below) tussling with younger male, G812 at Poole Harbour. The missing right foot is evident in this photo (photo by John Thorpe)

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G463 (below) with G812 (photo by John Thorpe)
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G463 at Poole Harbour on 21st January (photo by Pete Scott)

The post The explorer returns appeared first on Roy Dennis Wildlife Foundation.
 
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