Just some comments on your comments, Bruce. I’m
quite happy for anyone to disagree.
First, I do not entirely favour the zero-sum theory that
there is a finite number of Gang-gangs around Canberra (say 50), and if they
are somewhere else you won’t get any.
I would distinguish locally breeding birds from the winter
influx. As to the former, they like high hollows in mature trees, which
would limit breeding numbers and, I think, account for the very few local
breeders we have preferring the older suburbs of Canberra rather than the more
recently planted-up sheep-paddocks.
The winter influx creates the apparently large numbers. As
JMF says in BITAHC: “ flocks come down from the mountains to feed
in the trees or shrubs growing in the parks and gardens. Each year they
may be seen feeding in the ornamental pine trees and Pyracantha hedges in the
heart of the city”. This is the reason, perhaps, for the iconic
status.
From my observations, while they certainly feed in eucs they
relish buds and fruit (generally for seed) of exotic and out-of-area
plantings. I no longer get regulars around here since the
Cotoneasters were removed. They occasionally visit a neighbour’s
Chinese Pistacio until it is eaten out. The most regular influx that you
can set your calendar by is in a Griffith street planted with Crataegus
crus-galli. In past years I have seen as many as 40 in that street,
although this year the most I counted was 11.
In short I think the high numbers seen in Canberra are due to
(a) out-of-area plantings and (b) feeders.
Now, why do some areas not get them? Perhaps they like a
combination of tall mature eucs to roost and loaf in (they like yellowbox) and
reliable near-at-hand tucker. Like other cockatoos they learn where the
food sources are (and maybe need to learn about any new food sources) and
use them until they are exhausted.
Coming back to zero sum:
(a)
If the whole of inner-Canberra was put under high-rises
and car parks, would the present influx be diverted to the outer suburbs?
(Possible answer – maybe, but only if food availability and other
requirements were similar)
(b)
If all relevant conditions in inner Canberra were duplicated in
the outer suburbs would there be a corresponding increase in the GG influx?
(Possible answer - Surely not. That would require an increase in
breeding numbers which, one would think, are limited by hollows, territories
and availability of breeding-season food supply. Indeed there is a view that
overall numbers are decreasing.)
From: Bruce Lindenmayer
[
Sent: Sunday, 23 May 2010 12:37 PM
To: 'Canberra Birds'
Subject: [canberrabirds] GANG GANG CENTRAL
Last
week I visited a private back garden in a southern Canberra suburb, where I was
astounded to see some 5 or 6 feeding tables covered in sunflower seeds, with
the largest flock of Gang gang Cockatoos I have ever seen in the ACT. There
were more than 20 birds along with much smaller numbers of Little Corellas,
Sulphur-Cresteds, Crimson Rosellas and King Parrots. The Gang gangs were
extremely tame and approachable. Next to the feeding tables were very large
bags of seed.
The
elderly resident claimed that birds had been fed like this for more than 30
years, with up to 43 Gang gangs observed foraging at once. Other parrots
were "chased away".
There
were at least four birds in immature plumage, so one could assume that there
are now generations of Gang gang dependent on foraging at that site.
I
made the obvious point (diplomatically, I hope) that the birds might have
some problems when inevitably, they would no longer be able to be fed in this
way. However, I am sure that nothing will change in the
short term.
Whilst
the property in question is several km from Chapman, I now suspect there is a
reason why I have never seen a Gang gang here.
Given
the general scarcity of Gang gangs and their iconic status in the ACT, I think
this matter is unfortunate, although I don't know whether there is
anything that could be done about it.
