Here in Nova Scotia, life should be easy when dealing with skuas, we (mostly) get two – South Polar and Great. It wasn’t always so and it was really only in the mid-1980s that South Polar was realised to be the most likely skua to be encountered in our waters after a July record was sufficiently documented. That opened up all previous Great Skua records to natural debate. Establishing what species may be recorded is all well and good, but much skua identification is problematical and distant skuas may not always be attributable to a species. I would go further and say that this is a group where acceptable records are best validated by being documented with a decent photograph. I say this because, unfortunately, there is often contradictory information when it comes to identification of skuas and we do not yet fully understand skua plumages and biometrics well enough to make a fully accurate call for every individual seen without the luxury of taking a long, second look at digital images. Skuas can be the silent empids of the high seas!
You’d think that at least Great and Chilean Skua would be straightforward but the proclivity of the latter to interbreed with both South Polar and Brown Skua muddies the salty water. However, such individuals are probably rare enough within the main species’ breeding range as to be all but eliminated from our North Atlantic enquiries. Brown Skua may be a different matter and our pelagic senses would do well to be tuned into the possibility that this brute of a sea bird could find its way north in season. But this is a ‘might be’ and even South Polar Skua summer movements are not well known enough to be confidently stated. The mystery of why they are so readily encountered and identified at sea off the eastern seaboard of North America, and yet Europe has yet to satisfactorily document one is interesting. South Polar Skua should be off the UK and Ireland in late summer, where it would be a minority amongst the masses of Great Skuas and therefore, to some extent, more obvious. Personally I suspect that the, at the time overly cautious approach to new species adopted by the UK birding authorities, has much to do with the absence of South Polar from their UK list, but eventually a boatload of enthusiasts will fill their collective SD cards with acceptable images, and then gloat.
To further make the point regarding the identification of South Polar versus Great Skua, where borderline individuals are involved, a South Polar Skua from the September-24 2016 Brier Island pelagic was only tentatively called in the field, rather we relied on critical examination of the adequate photographs taken at the time to make a confident ID, a reasonable degree of caution. Obviously this will not always be the case and some skuas can be confidently identified in the field, obvious South Polars do look different from obvious Greats, but there is a broad range in between.
The Aug-04 2017 Pubnico pelagic encountered two skuas, one a ‘standard’, if tatty looking, South Polar, the other was best described as ‘interesting’ in that, biometrically at least (big bill), it was different from what we expect of a Nova Scotia South Polar, and so the possibility that it was a Brown Skua was floated. Differences in bill size between sexes in birds is normal, but Pubnico Skua#2 clearly has a corker, whereas the messy first bird and the one off Brier in September 2015 are, to all biometric intents and purposes, identical. With such a bird as Skua#2, consultation with other birders is a given and any, all, experienced comment is invaluable. Fortunately there is a wealth of experience out there in the wider birding world and so questions were posed and answered. Skua#2 is a South Polar albeit with a large bill, however, there is value in understanding the second bird better.
Fortunately this bird was well documented and the available photographs made requesting input much easier than relying on potentially subjective descriptions. I am indebted to Klaus Malling Olsen, Paul Walbridge, Jeff Davies, Rohan Clarke and Dick Filby for agreeing to take a look at the photos and for offering sage advice when dealing with South Polar versus Brown Skua; I have taken the liberty of including their comments in the text. Many thanks also to Claude King for his generosity in allowing me to use his excellent and instructive photographs of Brown, South Polar and Chilean Skua November 2016. Bravo for the shot of all three together. Any other photos used are mine.
And now the images.
These three heads are all Nova Scotian records of South Polar Skua. The first is from the aforementioned Brier trip of 2016, the middle one the Pubnico #1 bird of 2017 and the other is ‘Big Nose’ himself. I think you can see the differences mentioned.
Here are more shots of the Brier bird showing why we wanted to look at images of it before confidently calling it a South Polar. The initial impression was that it may be a Great, then better views placed doubt in most minds.
For reference this is Pubnico bird #1; a messy creature for sure but very instructive and well seen. The sea was much more benign on that trip than on the Brier one.
Here are a few shots of Pubnico bird #2 ‘Big Nose’, the moulting 1st year South Polar Skua. The lack of projecting toes beyond the central retrices in flight are an immediate pointer to South Polar versus Brown. The plumage tones, although mixed due to various stages of moult and the lack of bulk are further South Polar indicators.
These are Brown Skuas from Antarctica, specifically Carcass Islands, the Falklands 22-Nov, 2016; and two images from Salisbury Plain, South Georgia on 26-28-Nov, 2016 respectively ©Claude King.
This is a South Polar Skua from the South Shetland Isles 03-Dec, 2016 ©Claude King.
This excellent photo shows well the basic differences between Brown, South Polar and Chilean Skuas, from the South Shetland Isles 03-Dec, 2016 ©Claude King.
To summarise, a skua species with a large looking bill and intriguing plumage was seen off south-western Nova Scotia on Aug-04, 2017. It was identified at the time as a South Polar Skua. On review the images and following comments from elsewhere, it was suggested that the possibility of Brown Skua (or Brown Skua influence)was worthy of investigation. Comments from seabird experts were sought and generously given, and South Polar Skua (1st year) was confirmed. Pelagic birding in Nova Scotia is really only in its infancy and we are always grateful when more experienced observers are willing to share their knowledge and improve ours, only through inquisitive investigation do we learn.