Hi all
I sent these three notes to the editor of our local birding journal, Canberra
Bird
Notes, the other day. Maybe he will think they are worth publishing, maybe
not.
Anyway, I thought that Birding-Ausers may find them of interest and have
answers to the
questions I pose. I really loved the currawong/possum interaction!
David
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1. Early Nest-building Activity in a White-browed Scrubwren
On 23 July 1996 in the Rainforest Gully at the Australian National Botanic
Gardens,
Canberra, I observed a White-browed Scrubwren Sericornis frontalis engaging in
nest-building activity. Over a period of about ten minutes I saw it fly four
time to a
clump of vegetation. On each occasion it was carrying a large quantity of
plant
material in its bill. It disappeared inside the vegetation, only to reappear
moments
later without the plant material. It was a typical nesting site for this
species.
In the Canberra region the White-browed Scrubwren normally breeds in Spring.
Frith
(1984, p. 274) states that the breeding season in the Southern Highlands
extends from
September to January (although it is earlier at the coast where the climate is
milder).
The Australian Capital Territory bird atlas (Taylor & COG 1992, p. 133)
reports records
of nest building in the ACT from late August to late October. So far as I am
aware, the
1996 winter in Canberra is not unusually mild so it is unclear why this bird
commenced
nest-building so early.
References
Frith, H. (ed.) 1984, Birds in the Australian High Country, Rev. edn, Angus &
Robertson,
London.
Taylor, M. & Canberra Ornithologists Group 1992, Birds of the Australian
Capital
Territory: An Atlas, COG & National Capital Planning Authority, Canberra.
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2. A Pied Currawong Harassing a Ring-tailed Possum
The Pied Currawong Strepera graculina has a well-earned reputation for
harassing other
birds, often for no apparent reason. They are also known to harass domestic
animals.
On 25 July 1996, at approximately 1230 hours, at the Australian National
Botanic
Gardens, Canberra, I observed a Pied Currawong doing somthing similar to a
Ring-tailed
Possum Pseudocheirus peregrinus.
My attention was drawn to the Pied Currawong as it was vigorously tearing
leaves and
twigs from a thick clump of rainforest-type vegetation growing on a horizontal
branch of
a tree overhanging (and part of) the Rainforest Gully at the Gardens. Not only
was it
tearing off the plant material and dropping it, the bird also repeatedly jabbed
its bill
into the foliage. After observing this behaviour for a few minutes through 10
x
binoculars, I noticed a movement in the foliage some 20 to 40 centimetres
immediately
below the Currawong. It was a Ring-tailed Possum, apparently curled up in its
day-time
nesting place. The Currawong continued jabbing at the possum and tearing away
the
vegetation above it. After some ten more minutes of this, the possum uncurled
in a
sudden movement, jerking its upperbody towards the Currawong, which suddenly
took
flight, presumably startled by the rapid movement of the possum. The possum
then
resumed its former position deep in the foliage.
Why was the Pied Currawong behaving this way towards the Ring-tailed Possum?
The
currawongs are carnivorous but a healthy (if sleepy!) possum could not possibly
be a
prey item. It is unlikely that teritoriality would come in here, as the two
species have
totally different needs for food and territory. Perhaps the possum or the nest
smelt, to
the currawong, like carrion? Or perhaps it is simply yet another example of
the
inclination of Pied Currawings to harass other species of birds and animals,
even when
no survival advantage seems to be associated with such harassment?
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3. Red-rumped Parrots Benefiting from Sulphur-crested Cockatoos? Feeding
Twice in early July 1996 I observed flocks of Red-rumped Parrots Psephotus
haematonotus
feeding on the ground under Pin Oaks Quercus palustris in Kennedy Street,
Griffith,
Australian Capital Territory. While their usual foods are the seeds of grass
and
herbaceous plants, along with green plant material (Frith 1984, p. 175), I was
interested to investigate what they were eating at that location as they were
feeding on
all kinds of surfaces including hard bare soil, lawn and bitumen footpaths. On
close
observation it became apparent that they were feeding on the fruit of the Pin
Oaks. But
how can a small, grass seed-eating parrot possibly eat the very hard, 10mm
diametre
acorns?
For some days prior to this observation, large flocks of Sulphur-crested
Cockatoos
Cacatua galerita had been feeding on the Pin Oaks. They had no trouble
removing the
acorns from their stalks, cracking them open and extracting the seeds.
Apparently, in
the process a substantial quantity of seed had fallen to the ground where it
was
available to be eaten by the Red-rumped Parrots. The seed was already removed
from the
acorn and so was readily accessible to the parrots, as accessible as grass seed
and
similarly sized.
Here is an example of one species benefiting from the behaviour of another,
without any
competition for resources being involved.
Reference
Frith, H. (ed.) 1984, Birds in the Australian High Country, Rev. edn, Angus &
Robertson,
London.
_____________________________________________________________
David McDonald Voice: +61-6-231 8904 (home)
PO Box 1355 Voice: +61-6-260 9231 (work)
WODEN ACT 2606 Facsimile: +61-6-260 9201 (work)
AUSTRALIA E-mail: (home)
E-mail: (work)
"Things are more like they used to be than they were before"
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