Post-Katrina Jaeger/Skua (1 Viewer)

Birders,

I would be interested in your ideas as to the ID of this bird that blew into Tennessee (USA) with hurricane Katrina. Please see the link, below.

Thanks.

http://www.pbase.com/ol_coot/pomarineskua

Seem to recall briefly seeing some discussion of this on another forum. The pictures show clearly this is a catharacta skua, and it's certainly not any of the stercorarius jaegers. The very bulky body and broad wings with a rather triangular hand, together with the very broad and prominent white primary flashes on the upperwing (which almost reach the carpal) all show the bird to be a catharacta species. It might well be a South Polar, a species I'm not familiar with, but this is such a challenging family that it may be hard to ID the bird with certainty. Hopefully others can pass more informed comments.

Rgds

Greg

Yes its a Catharacta. I'm hard pushed to prove its not just a Great Skua

Please prove it! Having seen Pomarines and Parasitic skua as well as Bonxies, I can see this is a Catharacta and not a Stercorarius; but I don´t have experience with southern catharactas
-so looking forward to the answer...

The pale body, contrasting with dark underwings in:

http://www.pbase.com/ol_coot/image/48660209

...combined with the relatively thin bill:

http://www.pbase.com/ol_coot/image/48659885

...and pale nape:

http://www.pbase.com/ol_coot/image/48660117

...look good for South Polar Skua to me.

I agree with the caution of others - although it looks superficially like South Polar, I really don't think it is as clear-cut as this. There is also the possibility of Brown skua, which has occurred in the UK recently.

GV

jmorlan said:

The pale body, contrasting with dark underwings in:

http://www.pbase.com/ol_coot/image/48660209

...combined with the relatively thin bill:

http://www.pbase.com/ol_coot/image/48659885

...and pale nape:

http://www.pbase.com/ol_coot/image/48660117

...look good for South Polar Skua to me.

Click to expand...

Hi there... there is a load of difference between "looks good for", and "is provably alas". I must locate a British Birds article from a few years back that showed he variation in Bonxie (sorry [Great] Skua) and the perils of claiming South Polar Skua in the North Atlantic. The two UK Brown Skuas needed DNA analysis to prove what they were!

I've seen literally 100s of South Polar Skuas on West Coast pelagic trips over the years and I can assure you that this bird would not be questioned as such if it were seen here today.

How likely is it that a Bonxie would be picked up by Katrina and deposited in Tennessee? One needs to use a little parsimony here. South Polar is the most migratory of all skuas and the only one that is routinely found in tropical waters. I agree that Brown Skua is a possibility, but they are notoriously hard to tell from Bonxie. I've only seen one Brown Skua (just last month in Australia) and it did not show the contrasting pale underbody of the subject bird. This is a known obvious diagnostic field mark of light morph South Polar Skua.

Incidentally, it seems that Brown Skua may also occur in the North Pacific. Cf. the recent article by Steve Howell:

Howell, S.N.G. 2005. Revisiting an old question: How many species of Skua occur in the North Pacific. Western Birds 36:71-73.

The article points out how ageing the birds is critical to identification and suggests that molt state may be helpful in ageing.

But that's really besides the point. The problem is that some immature (and adult) dark morph South Polar Skuas can look like Brown Skua (or Bonxie). Those birds may not be identifiable. But the bird in question is a light morph South Polar and looks very distinctive once you know these birds.

The bird looks exactly like a typical light morph South Polar. It was storm driven from an area where only South Polar is likely to be.

You can argue that it's not provable, and caution is warranted, and that's fine. But I can also argue that science never proves anything; all it can do is disprove. I offered my opinion, a hypothesis that this is a South Polar Skua and suggest that those who think it might be some other species offer reasons to disprove my parsimonious hypothesis.

Hi Joseph,

Would not try to prove anyone wrong who has more experience than me on a species/pair. My post was just to warn of the caution required when identifying large skuas.

Experience here (where Great skua is relatively common) is that South Polar is very difficult to prove, and our NAtional rarities committees have procrastinated for over 20 years on admitting it to the British list (and in fact still haven't). This is despite some birds having photgraphs, and which looked very like the bird in the link.

This is where our British caution comes from - it's not an affront to your skills and experience.

All the best

Sean