Ospreys and White-tailed Eagles at Poole Harbour – a sign of hope 

Over the course of the first three years of the White-tailed Eagle project based on the Isle of Wight, which we run in partnership with Forestry England, we have become accustomed to the young birds living a highly nomadic lifestyle in their early years, dispersing as far as northern Scotland and in one case, continental Europe. However, as they become older, and approach breeding age, we expect them to return to the South Coast and establish territories within 50 km of the release site. The early signs are certainly encouraging. As reported in our last update, three-year-olds G274 and G324 are well-established as a pair on the Isle of Wight, while G405 and G471, both released in 2020, have been showing early courtship behaviour in West Sussex. Meanwhile five different birds have become regular visitors to Poole Harbour in Dorset, with one-year-old female, G801, an almost permanent resident since the spring. 

Poole Harbour, as the name implies, is a huge natural harbour, covering some 36km2. The northern shore is urban, but most of the southern and western areas, as well as the Arne peninsular, and five islands, including the well-known Brownsea Island, are much quieter. The harbour is extremely shallow, with an average depth of less than half a metre. These factors, coupled with abundant populations of fish such as Grey Mullet, mean that we expect it to become a favoured locality for White-tailed Eagles, and, potentially, a future breeding site. 

Roy and I have got to know Poole Harbour well over the past few years because it is the site of the Foundation’s ongoing Osprey translocation project, which we are running in partnership with local charity, Birds of Poole Harbour. This year has been a significant one for the project because a pair of Ospreys – male, 022, which we translocated from northern Scotland in 2019, and Rutland-fledged female CJ7 – have bred successfully for the first time, rearing two chicks. Although one was killed by a Goshawk after fledging it seems likely that the remaining youngster, 5H1, has now set off on her first migration. This is the first time young Ospreys have fledged from a nest on the South Coast of England for two centuries and so is a real milestone for the project. The video below shows 5H1 landing on the edge of the nest soon after fledging on 23rd July.

Poole Harbour’s location on the South Coast means it is also a prime location for Ospreys on migration, and numbers reach a peak during late August and early September as birds from further north move southwards. With this in mind, Birds of Poole Harbour have been running twice daily boat trips in search of Ospreys as well as a range of other species – White-tailed Eagles included – since 19th August. Knowing this would also be an excellent opportunity to observe the behaviour of G801 and any other eagles that were present, myself and White-tailed Eagle project officer, Steve Egerton-Read, have joined the Birds of Poole Harbour team on a number of trips over the past three weeks.

Monitoring the diet of the released eagles has been a key part of the project since the outset, and we have now amassed over 320 feeding records. However, such observations are hard to come by because White-tailed Eagles favour the sit-and-wait strategy for hunting; usually spending more than 90% of every day perched, quite often on the same favoured tree. Nevertheless, thanks to the work of Steve and dedicated volunteers, we have found that fish become increasingly important for the eagles as they become older, constituting up to 50% of the diet. This, we feel sure, is why G801 has remained at Poole Harbour for such an extended period, but monitoring her is not easy at such a large site. 

G801 photographed from a Birds of Poole Harbour boat trip on 1st September (photo by Mark Wright)

Our suspicions have been borne out during the boat trips, and we have twice seen G801 feeding on fish when the tide has been low or just rising. The Ospreys haven’t disappointed either with multiple birds seen on most trips, some catching Grey Mullet very close to the boat. We have, on occasion, also been treated to some close fly-bys by G801. On one memorable morning when I was on the boat, she flew almost directly overhead, providing amazing views and drawings gasps of excitement from those lucky enough to be on board. 

On another occasion Alison Copland filmed G801 flying close to the boat.

It is important to remember that Ospreys and White-tailed Eagles were once both widespread along the South Coast, before being eradicated by historical persecution. Whilst it is still early days for both projects, the fact that the two species can now be seen together once more at Poole Harbour is, I think, a sign of hope for the future. We are living in a time of great concern for the natural world but the return of these species shows that with a proactive approach to the restoration of nature, it is possible to make positive change. We are very grateful to the Birds of Poole Harbour team for organising the fantastic boat trips and for enabling 1600 people to enjoy the spectacle of these two species – sometimes interacting with each other – over the past three weeks. For me, the excitement of people on board when an Osprey caught a fish or a White-tailed Eagle flew past were always a highlight of the trips. 

A juvenile Osprey photographed from a boat trip on 1st September (photo by Mark Wright)

There are still spaces available on the final two Osprey cruises, which take place at Poole Harbour tomorrow. Birds of Poole Harbour also have a comprehensive programme of events taking place this autumn – check out their website here for more. You won’t be disappointed!  Steve and I will again be joining the boat trips when we can, particularly if the eagles continue to linger in the area.

We are also very interested to hear your views on the White-tailed Eagle project.  If you have a few minutes to spare please click on this link and complete our short survey.

White-tailed Eagle G816 and an Osprey over Lytchett Fields, Poole Harbour, on 30th August (photo by Mark Wright)

Tim Mackrill, 1st September 2022