On 6 Apr 23, a Forster's Tern was seen at the Somerset end of Sutton Bingham reservoir. This must have been frustrating for Dorset Birders as the Southern tip of the reservoir lies within the Dorset border. Talking to locals who twitched it, it stayed within Somerset until it was seen flying South & disappearing just after 19:00. However, it appears that nobody saw it in Dorset waters, as the Dorset end of the reservoir is difficult to see from public areas. I'm sure most Dorset Birders expected it to pop up in Weymouth the next day, but it just vanished. I was one of the few Dorset Birders who wasn't worried about its disappearance despite it being a Dorset Tick, as I was on the West Pacific Odyssey & I was out of a wifi signal until I reached Japan on 17 Apr 23. At that point I heard about its one day appearance and the lack of further sightings.
Fast forward to 23 Apr 23, when news broke that it had been relocated at Lytchett Bay in Poole Harbour. There had been a delay in the news getting out while the identification was being checked. The Lytchett Birders reacted quickly, but it had already departed. It was relocated that evening in the Brownsea Tern roost when it was nearly dark.
The next morning I joined Nick Hopper at first light at South Haven to scan the Terns flying in & out of the Harbour mouth: in the hope it would fly past. Mark & Mo Constantine and Paul Morton were out on a private bird boat to look over the Brownsea seawall, in the hope it was still on the lagoon. They couldn't check the cameras as the Birds of Poole Harbour cameras had all gone down overnight. Like Nick & myself, they drew a blank. Then their boatman said he had seen an odd-looking Tern on one of the buoys off Hamworthy the previous morning on their Birds of Poole Harbour Bird boat, but he didn't think to mention it at the time. That was a long shot, but worth checking given Hamworthy is just outside of the Lytchett Bay area. They checked it out & surprisingly, the Forster's Tern was sitting on the buoy again. Nick had already decided to head towards Lytchett & Hamworthy when the rumour broke.
I was quickly following him, but taking the land route rather crossing the Harbour mouth on the ferry. This proved a good choice as I quickly received an update on the car's hands free to say it had relocated to Lytchett Bay. I guessed that the new Rock Lea viewpoint might be a good viewpoint and headed there. I arrived to see it in the Bay, however, it was feeding on the far side of the Bay. Good enough scope views to add it to the Dorset & Poole Harbour Lists as a second for Dorset & first for Poole Harbour. By the time I got to the far side of the Bay, it had moved again & was still distant. I had seen it & didn't bother to stick around in the hope of photos.
After that, it settled in a pattern where it spent most of the day feeding somewhere in the top end of Poole Harbour, appeared sometime in the early afternoon on Brownsea for a few minutes, disappeared again for the rest of the day, until the Birds of Poole Harbour cameras or the Brownsea team confirmed it was in the Tern roost.
I still wanted to see it on Brownsea as Brownsea lies within the historic Isle of Purbeck & these days, that List is more important to me than my Poole Harbour List: as it includes the area where I do virtually all of my Birding. I could have popped over to Brownsea on the 25th, but I decided to wait for another day, as the 26th was my regular volunteering day on the Dorset Wildlife Trust Brownsea reserve. I was prepared to stick it out to late, as the volunteers can stay beyond the public hours, however, I'm glad to say I picked it up on the Boomerang Island about 14:30. It only dropped in for about three minutes before it was spooked & it didn't return when I left for the 17:00 boat. I was pleased that I didn't have to stay in the hope it dropped in to the roost before I would have had to leave for the 19:00 boat. I still didn't have any photos, as I had been focusing on trying to get my colleague with the video scope onto it & showing it to the other visitors in the Avocet hide. Still it was now on my Isle of Purbeck List.
Fast forward to 1 May when I was volunteering as an extra spotter on the Birds of Poole Harbour Bird boat. We were told it was sitting on one of the islands as we headed to have a sneaky look over the Brownsea seawall at the end of the trip. That news was announced about ten minutes before we reached Brownsea. Fortunately, it was still there & I picked it on sitting on one of the islands near to the Tamarisks that are visible from the Tern Island. Within a minute or two all the passengers were enjoying good views as the island is closer to the seawall, than it is to the Tern hide. Just to add some icing to the cream, Paul Morton picked up a Little Tern on the lagoon. Little Terns are just about annual on Brownsea, but can be fleeting in the visits. Last year, I failed to see one for the Isle of Purbeck Year List, despite twitching twice onto Brownsea when Little Terns were seen.
My next and last sighting of the Forster's Tern was back on Brownsea on my volunteering day on 3 May. It was briefly seen the following week, but I was in the villa having lunch between my volunteering duties & it had disappeared by the time I could get to the hide. The last sighting in Poole Harbour appears to be on 12 May 23 when it was photographed on the Brownsea lagoon & also seen feeding in Studland Bay off Pilots Point, Studland. I had looked for it inside the Harbour that morning, before a rapid departure to Portland Bill, when Dorset's first Moltoni's Warbler was found. Fortunately, I was there when it showed well for a couple of minutes on the only occasion it showed after it was released. I never saw the Forster's Tern at Studland, but will happily trade missing it that day by watching my first UK Moltoni's Warbler. There were a few subsequent reports of it being seen on Brownsea, but on several occasions before & after 12 May, this was down to some visiting birdwatchers misidentifying either the first Summer Common Tern or the first Summer Sandwich Tern that were both daily visitors to the lagoon.