Hello Bill,
In my experience there is little variation in Australian Raven calls from place
to place all over Australia, except for the SW of W.A. where they all sound
distinctly different in pitch (Listen on my website under Western Raven.)
However if you are talking repertoire, Australian Ravens have a call for almost
every occasion. When they are chasing a raptor (such as on call LS100104 on my
website) they sound almost hysterical whereas at rest (mild advertisement, at
rest call) the calls almost suggest the mood. When I hear that hysterical call,
I always look at the sky because I know there'll usually be a Wedgie or a
Little Eagle up there or sometimes a smaller raptor. The raven-like calls you
heard may have just been one you are not familiar with - for instance they have
a quite distinctive travelling call when flying high overhead which may be a
signal to the resident birds below that they are doing just that, travelling,
and have no territorial intents.
Little Ravens are a different story. Like Australian Ravens they do have a
repertoire, perhaps less distinctive to our ears, but there are other
variables. Birds from the interior are on average smaller than those from
alpine areas and to my ear, the bigger alpine birds have deeper sounding calls
. Little Ravens and Forest Ravens form a superspecies (that is they are very
closely related) and Forest Ravens, which are even bigger again have even
deeper calls. I like to think I've had more experience with our crows and
ravens than most people these days (I studied them with CSIRO and Ian Rowley
for nearly ten years) but I do admit that occasionally I hear a corvid call
that makes me think, as you did at Chum Creek. The ones I have found most
difficult were either from the Coorong/SE South Australia or from south
Gippsland, where both Little and Forest Ravens occur together. Corvids vary a
lot in size. Males are mostly bigger than females by about 10% but the birds we
used to call runts (the youngest of a clutch of five that only survive in good
seasons - normally they starve and fail to fledge) go through life as much
smaller birds and probably sound like wimps as well!! I did handle a bird once
which, on measurement was midway between Little Raven and Forest Raven and I
wouldn't be surprised if one day somebody finds these two species as a mixed
pair.
As somebody has pointed out certainly both Australian and Little Ravens can
occur at Chum Creek, and even Forest Raven would be a possibility - the Prom
isn't that far away and corvids do wander.
So you can see there are lots of variables and without hearing a recording of
your birds at Chum Creek, we'll never know. One thing I do know is that
Australian Ravens from Chum Creek will sound like Australian Ravens from
anywhere else in the eastern states. I am not aware of any local dialects. That
doesn't mean there aren't any - just that they are hard to discern. As with any
other passerines, most of their repertoire is learnt and like the vowel sounds
in humans, they would vary from place to place. If you really want to hear
regional variation in an Australian bird, go listen to the Grey Butcherbirds.
Regards
Graeme Chapman
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