Apologies for the delay in replying. Being back at work, I no longer check my
computer every day. Geoffrey's comments are right. I also draw attention again
to the very good synopsis Geoffrey wrote on this line some time ago about where
to find information about our local birds.
This, again is the relevant extract from my "Canberra Birds: A
Report on the first 21 years of the Garden Bird Survey". The text describes
a change in progress. It is clear and hardly surprising that the increase in
probably all population parameters of this species has continued, since the
release of my book as it was well underway for the last several years of the
period covered by the GBS Report. Therefore it can be expected that at the start
of every winter, we will get records of Satin Bowerbirds from new areas and
probably also progressively during summer we will get a few more sites with them
also in areas where they have only previously been present in
winter.
Satin Bowerbird Ptilonorhynchus violaceus
A species of forest that has, in recent years infiltrated the suburbs
adjacent to Stromlo forest. This was documented by Holland & Veerman (2000)
and Holland (2000). Even though this is a recent occurrence, the bird shows a
strong seasonal pattern to its presence in the suburbs. Therefore it is very
likely that it was originally an altitudinal migrant. From a July peak, numbers
drop smoothly during spring to a December minimum of about one tenth that number
and rise smoothly again in autumn. There were no records in Year 1, one record
in Year 2 and few in the next five years. In every measure of population the
species dramatically increased its prevalence in suburban Canberra in Year 8 and
it has continued this, though somewhat unevenly, since then. Many records
involve many repeat counts of similar numbers of individuals. The geographic
distribution of these records is interesting. Out of the 150 records at 40
sites, all but four records are from the suburbs on the south-western side of
Canberra, particularly Weston Creek suburbs. These sites are closest to Stromlo
forest and for Kambah records, close to the Murrumbidgee river corridor. In more
detail the first records were from Year 2 but the first records in Kambah are
from Year 9 and then regularly since then. One of the sites closest to the
Murrumbidgee river corridor (Site 213) on the north-west of the suburb, has had
the most sustained presence (with bowers built in this garden). Site 236 would
be a bit closer but first noted them in Year 19. This may be because this is a
newly developed area and the gardens there are still young. The next
western-most Kambah Site 152 got occasional records but it took till Year 17 to
get birds for a few weeks in succession. The two sites on the eastern side of
Kambah have only each had one observation of one bird. There are several sites
where (usually young) males have built bowers in gardens. The males will display
at them and some people have noted these as breeding records, whereas other
people did not. For this species, display including bower building, does not
constitute breeding, so these were ignored as breeding records.
The only GBS breeding records were in Years 19, 20 & 21. They have been
an "on" observation at Site 60, and a carrying food at Site 253 and the others
are all of dependent young from late December to late February. Mostly in the
south-western suburbs. These could have been hatched far away. There have been
other breeding events of this species in Canberra, as reviewed by Griffiths
& Holland (2001). Graphs on page: 103, Rank: 77, Breeding Rank: 52,
A = 0.10665, F = 12.42%, W = 29.3,
R = 3.425%, G = 3.11.
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