Black-winged Petrel, White Tern, False Killer and more: SOSSA pelagic of

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Subject: Black-winged Petrel, White Tern, False Killer and more: SOSSA pelagic off Wollongong NSW
From: Chris Corben <>
Date: Sun, 29 Jan 2012 22:11:43 -0600
Hi all

I think Short-tailed vs Sooty is a very interesting problem in many ways. In the hand they are always easy to tell, even ignoring measurements, just by the colour of the underwing. However, seeing that in a reliable way in the field is extremely difficult and hugely lighting dependent, so it's very easy to be mislead, even if you know exactly what to look for.

This is where digital cameras have made a huge difference. Even though a photo lacks a whole lot of important cues, it still represents a very unbiased view of something. The photons really did this, without any filtering by millions of neurons in the brain which are there for the very purpose of letting us see things which aren't there! This filtering is why we are so clever about what we see, but it still means that we largely see our lives through a succession of optical illusions!

Irrespective of all the ways in which Sooty and Short-tailed can appear to differ, they are still FAR more like each other than either is like anything else! While I can appreciate Nikolas' point about confusing the bird with a Wedgy, the fact is that ANY Sooty is always going to look far more like a Short-tailed than a Wedgy, once you see it well. I am sure you could briefly think a Fluttering looked like a Wedgy, but doing so would not be support for it being a Huttons, even though you could argue that a Huttons looks MORE like a Wedgy than a Fluttering looks like a Wedgy. The difference between a Sooty and a Short-tailed is so small compared to the difference between either and a Wedgy, that temporarily thinking it looked like a Wedgy just isn't really relevant.

I have had excellent opportunities to watch both Sooty and Short-tailed together on many occasions, and perhaps the best of these have been in California, where the argument has been expressed that you cannot tell them apart (but few would accept that). I have had plenty of examples where the difference between a Sooty and a Short-tailed was so obvious, that I started to wonder why I ever thought they were confusing. And then, just when feeling extra good about it, another bird would come along which made everything look confusing again, despite having excellent views. None of this is surprising, because it's just an inevitable consequence of the bell curve, which is so basic to all of biology.

The bird off Wollongong strikes me as more like a Short-tailed and Nikolas as more like a Sooty, and the photos are good. The fact that we cannot instantly agree on its identity when faced with photos this good is just an unambiguous testament to the genuine difficulty of this problem!

Cheers, Chris.


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