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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