My apologies for getting back to this topic
which was discussed in mid March by Geoffrey Dabb, Julian Robinson and Jack
Holland and others. I have been away.
In this long email I comment on, and ask
questions about:
- Changed roosting
behaviour of the Pied Currawong and also the King Parrot;
and
- Double brooding in the
Pied Currawong.
Please respond on the chat-line or to me
privately, for I would like to understand these situations more
fully.
Over many years (from at least 1977 when I
came to Canberra) Pied Currawongs (PCs) appeared to visit only one major roost,
probably in the Cotter pine forest, and it attracted birds from a wide area. By
standing at Scrivener Dam, it was possible to count the birds. My highest winter
count was over 3000 birds. King Parrots flew in the same general directions,
presumably also roosting in the pines. In those years birds of both species when
moving would have been registered by many observers in a number of
suburbs.
As was rightly mentioned, King Parrots did
not change their behaviour until the 2003 bushfires. In contrast, PC numbers flying towards the Cotter have
gradually declined over the years. A winter count a few years before the fires
yielded only 500 birds. Many birds no longer leave their territories or
congregate in smaller numbers at sites spread all over town, there is no need to
travel great distances each evening/morning. Many of these roost sites are
transient in nature. For example, the plane trees in Civic, Dickson and
elsewhere appear to be favourite sites (not just for PCs, also for Galahs,
Starlings and Mynas), but have to be abandoned once the trees have shed most of
their leaves. Small roosts can establish spontaneously. For example in my street
in Ainslie, mainly after a poor breeding season with failed nests, up to 20 or
so birds have roosted in the oaks in summer for a couple of weeks. No doubt
other roost sites in eucalypts or pine could be more permanent. The slopes of Mt
Majura are one such area, my highest count there in winter has been 300
birds.
From a fairly fixed situation with PCs using
one main roost we now have a very flexible, ever changing
situation.
From what I have seen in Civic birds will
call a lot before settling for the night, but then stop calling from one moment
to the next. Each plane tree is used only by a small number of birds, and they
will stay there even when you stand right under them, or move off
quietly.
The changes in roost behaviour in the
Currawong are obvious, and were largely independent of the bush fire, and
certainly were in train well before 2003.
Of great interest to me is what the King
Parrots are doing since their main roost went off in flames. I am aware of only
a small roost flight movement at Mt Majura, with highest counts around 100
birds. I assume we now have the daytime KP population splitting up in the
afternoon for their respective roosts. Do COG members know of other KP roost
sites?
Coming back to PCs: These morning post
roosting concerts are indeed impressive, and may last for some time (depending
on weather, i.e. fog etc.). I also often see small loose flocks of PCs in the
morning moving in a given
direction, either through the trees/gardens or often crossing wide areas
relatively high, giving the impression they have a target area in mind. In my
case, I see them either coming down from Mt Ainslie or heading that way, or
taking a different direction.
Geoffrey mentioned double-brooding. That is new to me and I
would like to hear more on that topic. What I have seen though is that PCs can
re-nest if their first clutch fails. The PC appears to be fairly sensitive to
wet weather while incubating or having very small young. Nests may be given up
(or not all hatchlings raised) under such detrimental weather, and re-nesting
could start once conditions are more favourable. This can certainly result in
dependent young being observed late to very late in the breeding season. HANZAB
mentions re-nesting after failure of the first brood, but only one case of
double-brooding (same nest produced fledgling in mid Sept. and late Nov. at
Berrima, NSW).
According to HANZAB nest building takes
from 2 to 4 weeks (here in Canberra I noticed that nest building can be
interrupted for pairs attempting to nest early [August] during cold/wet
spells), incubation 3 weeks, young
leave the nest aged 4 to 5 weeks, and it may take up to 7 weeks before they gain
full independence. Hence the total
breeding cycle takes 16 to 19 weeks. My guess is that conditions would have to
be very favourable before PCs in Canberra would be able
to raise 2 broods in a season (perhaps possible if 2 broods were to overlap).
But you never know, the PC has surprised us many times with the way it has taken
advantage of what this city and surrounding lowlands have to
offer.
Michael
Lenz
