To: "Geoffrey Dabb" <>,
Subject: Cohabitation
Date: Fri, 21 Sep 2012 22:39:03 +1000
I partly agree with Geoffrey, it is a matter of the relevant statistics,
but the question may be about whether would that be unusual in terms of
the two species either attracting or interfering with each other. If they
actively discouraged each other from nesting together, that would reduce
the chances. But some species actively like to nest in the same tree (e.g.
Leaden Flycatcher & Noisy Friarbird). But given the question and the two
species, provided they don't wish to use the same hollow, I for one, don't
think these two species would bother or attract each other.


Assuming this is a serious question, I would approach it as follows.
both cockatoos and wood ducks nest in tree hollows, so nothing unusual
there.  Next, both require large hollows which will be found only in
or old trees, particularly certain species of eucalypt.  It is reasonably
likely that an individual tree with one large hollow will have another
hollow.  I couldn't put a figure on that , but my impression is that at
least 20% of large-hollow-bearing trees would have more than one large
hollow.  I suppose the specific requirements of the two bird species have
been studied and analysed, and those SPECIFIC requirement might reduce the
number of qualifying two-hollow trees further, perhaps to something like 2
or 3 in an area of several hectares of woodland.  So there you have say
tree in 10 hectares that could potentially be occupied at the one time by
pair of cockatoos and a pair of wood ducks.  What are the chances of that
happening?  Frankly, I have no idea.  I cannot help thinking that the
would depend on variables such as the number of pairs of (a) cockatoos and
(b) wood ducks in the general area that might be on the look-out for
somewhere to nest.  That is information we are not given.   Obviously if
there were lots and lots of such pairs the chances of the same tree having
two nests of different species would be higher.

By the way, Martin, what was the other unusual thing?

From: martin butterfield 
Sent: Thursday, 20 September 2012 9:34 AM
To: COG List
Subject: Cohabitation

A local resident has enquired of me:  "I also noticed today near Gundaroo
both white cockies and wood ducks nesting in the same tree ( different
limbs) again would that be unusual ?"

In the ACT it would probably be unusual that a tree with 2 hollows hadn't
been felled on orders from TAMS lawyers.  However in the less litigious
environs of Gundaroo would such behaviour simple represent two des res
occupied and them suiting different species?

Martin Butterfield

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