Re: FW: [canberrabirds] Cohabitation

[martin butterfield <>]

It wasn't that unusual (this year).  A flock of 50 European Goldfinches.  A couple of years ago it would have been exciting, but since the drought broke largeish flocks of finches have been quite frequent in this area.

WRT to the matter of hollows I suspect the enquirer was wondering if there was anything resulting from (at a general level) species A occupying a hollow that might cause species B to avoid the area.  

Martin

On 20 September 2012 10:11, Geoffrey Dabb <> wrote:

Assuming this is a serious question, I would approach it as follows.  First, both cockatoos and wood ducks nest in tree hollows, so nothing unusual there.  Next, both require large hollows which will be found only in mature or old trees, particularly certain species of eucalypt.  It is reasonably likely that an individual tree with one large hollow will have another large 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 one tree in 10 hectares that could potentially be occupied at the one time by a 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 answer 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: [canberrabirds] 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 being occupied and them suiting different species?

 

--
Martin Butterfield

http://franmart.blogspot.com.au/

 

--
Martin Butterfield

http://franmart.blogspot.com.au/