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Con,
your morning flock of Little Corellas may have come from
the ANU roost where actually both species roost together (I think Leo Berzin
provided to the chat line some figures on totals for both species from a mid
winter count, last year)). Of course, we do not know the size of the
'catchment area' for this population coming to roost at the ANU. To judge by the
L. Corellas I see crossing Lyneham in the morning (often in various directions),
they may well travel some distance to their day-feeding grounds.
Regarding competition between the 2 species, due to body
size they have different cavity requirements. The smaller L. Corella
may have better chance of finding a suitable hollow (or may find a hollow in
younger trees) than an SCrCockatoo may be able. The L. Corella may then be more
likely to be in competition with the Galah, as was already mentioned in another
message.
Also many thanks to Martin B for the various graphs,
including the latest set. Great that Martin can draw from the full spectrum of
GBS data, and hence can give a most comprehensive picture.
Michael Lenz
Sent: Sunday, April 01, 2012 9:47 AM
Subject: Re: [canberrabirds] Little Corella
Martin
Looking at those graphs it seems to me possible to
hypothesise that if the later years are the start of a trend, then the Little
Corellas are gaining while Sulphur-cresteds are declining, relatively. I suppose
that one of the variables is how much the Little Corellas and Sulphur-cresteds
are recruiting from outside.
What the graphs do show is what a wonderful
resource long-term data collection by way of the GBS is.
Con
On
1/04/2012 9:39 AM, martin butterfield wrote:
Con
I think the answer is probably not.
The attached GBS based graph shows that the Corellas have - as you
indicate - made a massive increase in the recent past, but while the Cockies
have a slight downward trend from a high point, they are still a long way in
front. The graph also served to jog my mind about how far Cockies have
increased in the past 30 years.
In Ian Fraser's latest book he wonders
if Corellas will overtake Galahs (the latter having themselves only arrived in
this area in the last ~60 years).
Martin
On Sun, Apr 1, 2012 at 9:00 AM, Con Boekel <m("boekel.com.au","con");
CTRL + Click to follow link"
href=""
moz-do-not-send="true">> wrote:
This morning a flock of 170 Little Corellas flew over Haig Park
in Turner. It is obvious that Little Corella numbers in Canberra have
climbed over the past quarter of a century - certainly in the Inner North. I
often notice Little Corellas feeding in the same trees as Sulphur-crested
Cockatoos - on the same food.
The question I have is this - are our
Sulphur-crested Cockatoos declining as the Little Corellas
increase?
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