2021 is proving to be an encouraging year for the Poole Harbour Osprey Project, which we run in partnership with Birds of Poole Harbour and Wildlife Windows.
The long term aim of the project is to restore a population of Ospreys on the South Coast of England, where they have been absent for 200 years. This involves the translocation of young from nests in Northern Scotland. You can learn more about the project in our podcasts here.
Young Ospreys usually return to the UK for the first time in their third calendar year, and so this spring we were hopeful we would see some of the birds released in 2019 back in Dorset for the first time. Satellite tracking studies have shown that young Ospreys wander widely when they first return, but they usually visit their natal site (which in the case of the translocated birds is the release site) at some point during their first summer back in the UK. A key part of this behaviour is to prospect potential breeding sites, and, as a result, young birds often intrude at active nests. The movements of satellite-tagged male Rothiemurchus when he first returned to Scotland in 2011, is a good example of just how far young birds wander before they establish their own nest site.
In the early years of colonisation, it is usually males who establish territories, before attempting to attract a mate, but the difference for any returning male to Poole Harbour this year, was the presence of an unpaired female. CJ7 fledged from a nest in Rutland in 2015 and has returned to the Poole Harbour area each summer since 2017. It seems that the presence of translocated juveniles in the area has been a key factor in her settling in Dorset. She paired with a translocated bird, LS7, in 2019 but sadly the young male failed to return from migration last spring. Unperturbed, CJ7 has remained faithful to the same artificial nest for the past two summers and has laid unfertilised eggs on each occasion, demonstrating her eagerness to breed.
As those of you who have watched the Birds of Poole Harbour live stream this summer will know, there was great excitement on 18th May when CJ7 was joined at the nest by 022, a male that we had translocated from a nest in Strathspey in 2019. The two birds paired up immediately, and were seen mating regularly. It is highly unusual for two year-old Ospreys to breed, but we were hopeful that CJ7 may lay eggs in late May. That did not happen, but the two birds have remained together since, and, assuming they both return from migration, we are hopeful that they will attempt to breed next spring. What is not so certain is with nest they will choose – in recent weeks they have been seen at various artificial nests around Poole Harbour, and have been interacting with this year’s newly-released juveniles, even perching on nests with them.
Whilst the key long-term aim of the project is to restore breeding Ospreys to the South Coast of England, early evidence is showing that this new population will also help to link different populations of Ospreys. The presence of translocated birds in and around Poole Harbour has led to CJ7 taking up residence in Dorset, while a female that we translocated to Poole has bred successfully in Wales for the first time this summer. 014, a female released in 2018 has bred for the first time this year at a nest at Pont Croesor in the Glaslyn Valley near Porthmadog in North Wales. She raised a single male chick (ring number 494), with a four-year-old male, Z2 or Aeron, from the Cors Dyfi nest in mid-Wales. Meanwhile a second female, 019, released at Poole Harbour in 2019, was also seen in Wales earlier this summer. She was captured on camera when she visited the nests in the Glaslyn Valley on 5th June. This was the first sighting of her back in the UK, although she was seen on a number of occasions at Gunjur Quarry in The Gambia during her first winter and again in March this year. She was subsequently seen at Cors Dyfi further south in Wales on 30th June and possibly again on 5th July. This demonstrates how widely young birds wander when they first return; helping them to develop important knowledge of where other Ospreys are breeding. It will be very interesting to see if and where the young female appears next spring. Research has shown that male Ospreys typically breed close to their natal site, but females often disperse further, and so it is possible that 019 may follow 014’s lead and also return to Wales in future years to breed. Or should another translocated male return and set-up territory at Poole Harbour, we may yet see her back in Dorset.
A key element of the project at this early stage is the continued release of young birds, and during July we translocated a further ten juvenile Ospreys from nests in Moray and Highland. The young Ospreys are collected under a special licence issued by NatureScot from broods of two or three and then held temporarily at Roy Dennis’s home near Forres, before being transported by road to Dorset. You can hear more about our work collecting Ospreys by listening to one of our podcasts from 2019 here.
Once the birds had arrived at Poole Harbour on 15th July they were immediately moved into holding pens and monitored by the Birds of Poole Harbour team. CCTV cameras enable the birds to monitored closely during this period and released when appropriate. The first five birds were released on 2nd August with the remaining younger birds making their first flights ten days later.
The post-release period is critical in the imprinting process because it is when the young Osprey learn that Dorset is home. They generally remain close to the release pens for the first ten days, before venturing further a field and exploring the wider landscape. Fresh fish is provided by the team on a daily basis in order to replicate what happens at natural nests, and so even when the young birds make longer exploratory flights, they usually return in the evening to feed. Most young Ospreys do not catch their own fish until they depart on their first migration, and so the fish provided by the project team is essential in helping the birds to get into the best possible condition for the long flight south.
In the last few days the juveniles have been seen in the presence of CJ7 and 022. At Rutland Water there were instances of non-breeding adults feeding translocated juveniles, and we wonder if that may be repeated in Dorset this summer. Both 022 and CJ7 tolerate food-begging juveniles perching on artificial nests with them, and it will be interesting to see if they respond to the incessant food-begging, by providing fish. Regardless, the presence of the young birds will further strengthen the very strong bond that both CJ7 and 022 already have to the area.
This year’s juveniles are likely to remain at Poole Harbour until early September before setting off on their first migration. An excellent way of seeing them before they depart is to join one of the Birds of Poole Harbour Osprey cruises. You can find out more here.
