I happened to be pottering about Raby Bay [a canal estate south of the
Brisbane River] on Sunday and noticed two dark, hunched stalking birds
on the rocky flats. My immediate thought in the strong sidelight was
that both were mangrove bitterns / striated herons. However, I noticed
that I couldn't make out the black cap on one of the birds - rather it
was a relatively uniform leaden colour. When it extended its neck and
spread its wings in the course of its hunting, it was obvious that it
was a dark morph reef egret. The other bird was a bittern - probably a
dark morph but it kept its back to the sun, so it was hard to be
certain. Interestingly, some people I showed pix of the two birds to
didn't realise that they were different species.
Anyhow, I'm sure this has been discussed at some time, but what is
supposed to be the basis for the distinction between egrets, herons and
bitterns? It is obvious that there are egrets that are herons, herons
that are egrets, and herons that could easily be called bitterns. The
white-faced heron is an Egretta, the reef egret is more heron-like than
the pied heron, and the striated and rufous night herons are rather
bittern-like with their short necks and hunched posture.
Clearly, there are species that get around with an upright posture and
strike downwards, and species that are hunched and strike horizontally.
Presumably the egrets were white upright species [I suspect that reef
egrets were named on the basis of the white morph], herons were upright
species that weren't white, bitterns were furtive hunched species that
lurked in the vegetation, and that Nycticorax caledonicus and Butorides
striatus were labelled herons rather than bitterns because they come
out into the open and move about while hunting. Their bittern-like
characteristics though, are probably why Pizzey and Knight put them in
with the bitterns rather than the herons.
Regards, Laurie.
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