Long-tailed Skua - Bay of Islands

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sav
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Long-tailed Skua - Bay of Islands

Postby sav » Mon Apr 16, 2018 9:50 am

Hi all,

Ross Silcock has alerted me to a photo of a Long-tailed Skua off Cape Brett in the BoI last week (11 April) - the eBird link is https://ebird.org/view/checklist/S44484406

Originally described as a Wedge-tailed Shearwater (??) it is now captioned as a Parasitic Jaeger ( aka Arctic Skua)..

cheers
Sav Saville
Wrybill Birding Tours, NZ
Great Birds, Real Birders
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RussCannings
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Re: Long-tailed Skua - Bay of Islands

Postby RussCannings » Mon Apr 16, 2018 7:25 pm

Cheers Sav,

So why isn't this a Parasitic/Arctic Skua? Appears to be a dark morph adult which is extremely rare in Long-tailed, there appear to be pale shafts visible in the underwing, the bill seems biggish for LT (and possibly bicoloured) and the tail doesn't seem to rule out Arctic in central primary projection.

Russ C
Steve Wood
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Re: Long-tailed Skua - Bay of Islands

Postby Steve Wood » Mon Apr 16, 2018 8:16 pm

Hi Russ,

If the pic was not so underexposed I think it would be a more obvious that it is indeed a Long Tailed (for me anyway).
Only three pale primary shafts visible on the upper wing , no visible marking on the underwing apart from one smallest glint on one primary.I would expect more even on the darkest Skua. Hugely variable I know.
I confident, if it was "lightened up " you would see much better that is actually steel grey coloured above with a dark trailing edge to the upper inner wing which would be diagnostic alone. Bill and head shape fine.
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sav
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Re: Long-tailed Skua - Bay of Islands

Postby sav » Tue Apr 17, 2018 10:02 am

Hi Russ,

Thanks for the message. To my mind this just looks like a Long-tailed, and I know it is hard to get jizz from a single shot, but this one has it for me.

Just ignore the colour for a moment (because I think the exposure is clouding the issue) and there is the silhouette of a Long-tail. Small head and bill, that hunched appearance which is just right, broad based wings with slightly rounded tips (which is how they often look even though no literature will support that!) and a tail that is proportionally way too long for Arctic.

The 2 and a bit white upperwing primary shafts are more or less diagnostic and the single underwing shaft says nothing. I think that lightening the image will probably show that the belly is pale, and the trailing edge of the upperwing is dark. So maybe not a dark morph adult at all?

If the guy has any other, even out of focus, shots they would help.
Sav Saville
Wrybill Birding Tours, NZ
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RussCannings
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Re: Long-tailed Skua - Bay of Islands

Postby RussCannings » Fri Apr 20, 2018 7:55 pm

Hi Sav,

I contacted the observer was able to send me some lightened up additional photos. To my eyes they seem to show a dark/intermediate adult (He did not note any white belly in the field) with over 3 white shafts on the upperside and definite covert contrast in the underparts along with a nape pattern unlike typical LTs. Tail also looks shorter with more side-on angle. Whaddya think?

Parasitic Jaeger (1 of 1)-2.jpg
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Parasitic Jaeger (1 of 1).jpg
Parasitic Jaeger (1 of 1).jpg (103.05 KiB) Viewed 494 times
Steve Wood
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Re: Long-tailed Skua - Bay of Islands

Postby Steve Wood » Fri Apr 20, 2018 9:11 pm

Hi Russ,
Attached the same images lightened, and I still think that it appears greyer to my eyes and shows the dark trailing edge a bit better to the upper inner wing as suggested.
The pale primary shafts show more than the standard 2/3 which would be the norm, but they can show 4/5 on the rare occasions.
However I would have liked to see the bill two toned which I cannot see.
Parasitic Jaeger %281 of 1%29-2.jpg
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Parasitic Jaeger %281 of 1%29.jpg
Parasitic Jaeger %281 of 1%29.jpg (106.65 KiB) Viewed 478 times
Steve Wood
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Re: Long-tailed Skua - Bay of Islands

Postby Steve Wood » Sun Apr 22, 2018 10:30 am

I have since given this bird some serious attention and I think Russ is correct and it is more likely a dark phase Arctic Skua.

Apart from the greyish wash that I based most of my casual thoughts on, all the other key features when scrutinised are not really that strong for LT.Skua.
Dark phase LT skua are extremely rare, and even though it is stated (Klaus Malling Olsen : Skuas and Jaegers of the world) that they can but rarely have more than three pale primary shafts on the upper wing, I think that it is unlikely to be the case here. Can't find any examples either for comparison. IF it was indeed a dark ph. LT Skua,it would make this an incredibly unusual bird. Possible.... but unlikely.


Welcome any more thought on this bird. Well done Russ.
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sav
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Re: Long-tailed Skua - Bay of Islands

Postby sav » Sun Apr 22, 2018 2:51 pm

Hey,

Big slice of humble pie for me. Now that these are lighter, and all those white primary shafts are showing, I dont see how it can be anything but an Arctic.

Hats off to Russ. It had me well and truly fooled.

cheers
Sav Saville
Wrybill Birding Tours, NZ
Great Birds, Real Birders

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