Finders in the Field: South Polar Skua, Scilly, July 2023
By Bob Flood
This past weekend in the southwest of England has been sensational for seabirders and seabirding. The numbers of large shearwaters seen off Cornwall is staggering and the Corns had a Fea’s-type Petrel, too. We had a share of the action at sea on our Friday to Monday Scilly Birder Special Pelagics. All told, we saw 5 Scopoli’s, 5,400 Cory’s, 1,810 Great, 217 Sooty Shearwaters; 2 Long-tailed and 4 Arctic Skuas; 3 Sabine’s Gulls; 68 Wilson’s and 380 European Storm-petrels; Cuvier’s Beaked and 3 Minke Whales; numerous Short-beaked Common Dolphin, and tagged and released a Blue Shark. We set daily count records for two species; 39 for Wilson’s on Monday and 3,500 for Cory’s on Sunday.
Ah yes, and then there was that Monday evening skua.
At 18:37, I heard several people call, “Skua.” The skua flew in from the east at about 7 meters height. As it flew in head-on, I thought, oh good, a Pomarine Skua, we haven’t seen one this weekend. At close range it banked to the cry, “Bonxie.” I was a bit taken aback by this as, clearly, I was wrong, the skua wasn’t a Pomarine. The skua made a half-hearted attack on a juvenile gull, passed around the bow of the boat, flew around in a kind of circle, and then drifted off to the west. I watched it to the last moment.
Meanwhile, all else on board were back to business, with Cory’s passing at eight per minute, Great Shears at a slower rate, and yet another Wilson’s racing in from downwind, heading to our smelly oily slick, edging the count of Wilson’s ever-closer to the Scilly record and beyond. With such excitement, why would anyone want to spend time on a Bonxie?
Well, I had noticed that the bird was moulting inner primaries, its plumage had a distinctly cold greyish tone, and the bird was rather stand offish (plus other features given below).
None of this clicked with Bonxie. For a start, Bonxie’s normally harass the gulls in multiple attacks, often sneaking away from the boat while planning their next stealth attack. They’re mean. In this respect, I remembered Marcel Gil Velasco’s excellent piece on South Polar Skua ID (https://subalpinebirding.com/blog/south-polar-skuas-at-a-glance) in which he noted that South Polar Skuas tend to be stand offish and do not hang around boats for long. So true in this case.
Regarding moult, I have memorised the moult timing chart of Newell et al. (2013). I was able to roughly calculate the moult score, as I had noted p1 and p2 were both new, with a gap in which p3-p4 are found, but in this case were either dropped or had just started growing. New feathers score 5 each, dropped or in pin feathers score 1, and early growth scores 2-3, giving a total moult score of 13-14. I plotted this in my mind on Newell et al’s (2013) moult timing chart that compares Great and South Polar Skuas. The moult score combination fell in the region of the chart unique to an older South Polar Skua (second moult cycle or older). And the bird had a cold greyish tone and the scapulars lacked markings that you would expect on Great Skua. I was beginning to feel a little shaky. I needed to see photographs
I was stood on my own on starboard side, the photographers were lined-up along port side, shooting birds arriving from downwind. It was quite amusing, like a firing range at a country fair. Maybe none wanted to be interrupted as the next Calonectris shearwater might be another Scopoli’s and the Wilson’s were flying in thick and fast. Hmmm, I thought for a moment, and then told myself, “This is an ornithological emergency!”
I edged over to the photographers, all of whom are sound birders too, and asked to see photographs of the skua. The guys were fine about it, helpful, and curious. Elliot Cornelius, Finley Hutchinson, Scott Reed all had photos to share. Not easy looking at shots on the back of a camera, in a stiff 18 knot breeze, boat rolling, with moisture in the air. Nevertheless, the photos revealed that the upperwing-coverts were fairly uniform with few marking (on fringes, not along shafts). The body was fairly uniform with scalloped sides. The head and bill looked jaeger-like, not Bonxie-like.
I explained my thoughts about South Polar Skua and said that ultimately the photographs must be seen on a computer screen as this was a huge call. There was no rush. After all, this evening no one was going to swim 10 kilometres south of St Mary’s at 22:00 in the now 20 knot wind.
I had a bit of a chat about the ID with my pal Ashley Fisher who shared my thought processes and was supportive of the ID. Higgo (John Higginson), Joe Pender and I talked about my two remaining concerns, that the bill was large and the bird lacked a pale nape collar. As we disembarked the famous MV Sapphire, there was a palpable sense of excitement among the birders that, not only had we seen a Scopoli’s Shearwater, a mega, on this trip, but most likely we had seen a South Polar Skua, making two megas on one pelagic (let alone the 39 Wilson’s and so on). Nozzer (Bob Dawson), Steve Holloway, and Big Al (Alan Hannington) joined in the chatter as we walked along the quay heading for home.
I arrived home about 22:30. My beloved Mandy made me a strong cup of tea with 2 digestive biscuits and, having experienced ornithological emergencies numerous times over the past 47 years, decided to retire to bed. Sam Viles kindly forwarded photos of the skua from his pals that were on board, Scott emailed his photos, and I had access to Ian Bollen’s photos. By 01:30 next morning, I had written my notes, and found photos of South Polar Skuas with large bills and a dark nape. I prepared an email to send to the knowledgeable Dick Newell and to my good friend and supremely talented birder Dani López-Velasco (both of Newell et al. 2013 fame).
Hi
Attached photos are of a skua seen on the evening of 31 July off Scilly. My notes are also attached. I am thinking that it is a South Polar.
Primary moult timing puts it 'between lines A and B' albeit much nearer B. It is cold toned and the upperwing and upper side are fairly uniform with a few markings but they are on fringes of feathers, not shafts. Other support characteristics and observations are in the attached note.
The bill looks quite thick, though I have seen photos of South Polar like this. Wondering if a small head accentuates the size of the bill. There is only a hint of a nape, but at least a hint.
Would be grateful for your opinion as this is a huge mega for the UK.
It's 01:30 in the morning and I am beat and must sleep.
Cheers matey,
Bob
That done, I slipped into sleep in my armchair and then out of sleep at 05:30, still in my armchair. I was too excited to sleep, but my correspondents were fast asleep. Time ticked by, slowly. My correspondents were greeted in bed by my email and very kindly replied right away. They ran through several interesting aspects of South Polar ID and gave me their thumbs up.
With a slow hand and contented smile, I typed into Chris Langsdon’s Scilly Birding WhatsApp group: “South Polar Skua on last night’s pelagic.” I omit here the second sentence of the WhatsApp message, as I have managed to get to this point using polite text.
Bob Flood
2 Aug 2023
scillypelagics.com
Reference: Newell, D., Howell, S.N.G., & López-Velasco, D. 2013. South Polar and Great Skuas: the timing of primary moult as an aid to identification. British Birds 106: 325-346.
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