Rarity finders: Forster's Tern in Somerset


Sutton Bingham Reservoir (SBR) sits on the Somerset-Dorset border, a couple of miles south of Yeovil, and was where much of my formative birding was done in the early 1980s. At this time, SBR was a great local patch, supporting regionally important waterfowl populations and turning up a variety of scarce and sometimes rare species. 

Fast-forward 40 years, and SBR is again my local patch, but it's now a very different place, having undergone many changes. Perhaps the most damaging change has, in my opinion, been the introduction of Common Carp, and it is now evident to even the most casual visitor that most species of waterfowl are absent. I've been trying to persuade Wessex Water, which owns the site, to acknowledge and address the ecological problems for some years now, but progress is glacially slow. So, while SBR is not the most exciting place, it's close to home and I still enjoy going there. It does also still occasionally turn up interesting species. 

There are a few local birders who visit the site on a near-daily basis and, on 6 April 2023, with news of birds of local interest on my mind (there had been an Osprey and an Egyptian Goose the previous day), I set out on another hope-fuelled visit, arriving at about 1.30 pm. 

Reality quickly kicked in – at the north end, a single Eurasian Coot was the highlight! This individual had arrived the previous day and was remarkably the first to be recorded at SBR in 2023. With nothing else to see I drove to the south end and I scanned up the arm of the reservoir. I was excited to see a distant tern, way off to the north. As nothing had been reported on our WhatsApp group from earlier in the day it seemed likely that the tern was a recent arrival. 

Now, any tern at SBR is notable and in spring even Common Terns are rare, so this needed to be investigated fast before it disappeared. I quickly headed towards the bird but lost it from view. A few minutes later I was relieved to relocate it sitting on a buoy. It was still a long way off and, with no tripod, I rested my 'scope against a tree to try and identify it. I was surprised to see it appeared to be in winter plumage, having a white crown and nape and distinct dark patches around the eyes, and I assumed it was an immature Sandwich Tern – a very odd record at SBR and a bird the other locals would want to see. Terns don't usually stay for long so I hastily put a WhatsApp message out to the group saying an immature Sandwich Tern was present ... seconds count in these situations!

Britain's last Forster's Tern was in 2016 – and Somerset's only other record as long ago as 1987 (John Wall).

I continued towards the bird but, before I could get a better view, it was flushed by a sailing dinghy and was lost from view behind some trees. I now half-expected that it would be gone and Ash Warne, in response to my message, was on his way. Fortunately, a few minutes later it reappeared back on the buoy and I was now closer and able to have a better look. 

I was immediately concerned that my earlier identification was wrong – the black on the head was largely restricted to discrete but striking eye patches and I could now also see it had reddish legs and lacked a 'spiky' nape, so it didn't fit Sandwich Tern. It had a bull-necked, large-headed look and a broad-based dagger-like bill which, along with the eye patches, didn't fit Common or Arctic Tern either. It was definitely a first-winter bird: it had subtle pale fringing to the wing coverts and darker-centred tertials. 

I was now really perplexed and thinking 'what is this?' ... I knew that Forster's Tern in winter plumage showed this distinct head pattern but this seemed vanishingly unlikely and I held that thought back! I wondered if it could be an aberrant first-winter Sandwich Tern or was there something else I was overlooking, such as an unusual form or variant of another common species.

I wracked my brain but nothing came to mind and the thought it might be a Forster's Tern was gaining traction. At this point I was getting good views of it settled on the buoy and, with hindsight, the identification should have been quite straightforward, but context was everything – I was on my own, with no reference material and nothing to compare the bird to, I was also inland and it was early spring, and my recollection of previous Forster's Tern records were all of autumn or winter birds. Perhaps most importantly I was at SBR and having been birding here thousands of times before I 'knew' that something as rare as a Forster's Tern just did not happen here – I simply couldn't override that instinct!

The tern was well appreciated by visiting birders before its departure that evening (Andrew Jordan).

A sailing boat then flushed the bird again and I got good flight views. It looked daintier than Sandwich Tern with a more deeply forked tail and its buoyant action was more like a Common Tern, but its 'front-heavy' jizz, stout bill, dark eye patches and pale overall appearance said it wasn't that species. It had dark tips to the outer tail feathers, further indicating immaturity. From below the primaries could look translucent and they had dark tips, forming a distinct dark trailing edge. 

It headed off down the arm of the reservoir and I again feared this would be the last I would see of it. My heart rate had increased and I was now struggling to accept what I had seen – Forster's Tern seemed so improbable, and with the bird now potentially departing and me as the sole observer, I was feeling a bit sick!

I had taken a couple of record shots with my pocket camera but hadn't even looked to see what these showed when I noticed a missed call from Ash who, having arrived and not seen either me or the bird, had assumed it was gone. I phoned him back and said I was watching it disappear down the arm of the reservoir. Ash soon approached and I waved to hasten him and pointed down the reservoir, indicating it was flying. Ash was still expecting to see a Sandwich Tern, so I shouted that I wasn't sure what it was – but that it wasn't a Sandwich Tern or Common Tern! 

Fortunately, it returned towards us and then very helpfully it landed on a close buoy. Ash independently raised the possibility of Forster's Tern and we discussed its identity. I put a message out to the WhatsApp group saying it looked closer to Forster's Tern than anything else. Ash managed to get some good phonescoped video of it on the buoy and we continued to discuss the ID. 

Having someone else to confirm that I wasn't seeing things was a major relief, and while we concluded that it had to be a Forster's Tern, my irrational reluctance to accept the facts was still getting the better of me and I wanted more time to be absolutely sure before putting the news out, as clearly this would be of major interest. To Ash's great credit he then posted his video, on the WhatsApp group and on twitter, as a 'putative' Forster's Tern, and soon some positive responses were coming in and the news was out!

Peter's find marks the first inland record of Forster's Tern in Britain (Mike Trew).

The bird soon disappeared to the north end of the reservoir, where we relocated it 10 minutes later. Here it continued to show well, resting on buoys, and fishing off the main causeway. Other birders were soon arriving and watching it and fortunately it stayed for several hours, allowing many people to see it. I later heard that it appeared to depart to the south at around 7 pm.

It's interesting to speculate about this occurrence and I presume a likely scenario is that it had arrived as a young bird in the eastern Atlantic during the previous autumn, then overwintered somewhere to the south in Europe or West Africa, and was now on its northbound spring migration. It just goes to show that anything can turn up anywhere – the magic of patchbirding!

Written by: Peter Akers

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