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Hi Alan, Anthony, Carol and David,
Re Glossie food in the central west of NSW: Thanks
for the interesting info everyone. It all goes to give a clearer picture of the
needs of the Glossy Black-Cockatoo.
I get thoroughly confused by the
Allocasuarina/Casuarina distinctions - except for remembering that Allo has
black seeds and Cas has grey.
All mature casuarina cones will open their valves
to discharge their seeds if picked and put into a paper bag for a while. The
time depends on the species, but it's usually just a few days. Left on the
plant, cones will ripen and discharge seeds from opened valves of woody
cones. Glossies only eat cones that are "pre-ripe" - that is, when the seeds are
developed, but the cones are still fairly soft and sappy.
There are huge variations in cone behaviour, such
as between the two shrubby casuarinas in Goonoo (43 kms N/W of Dubbo) and Buloke
- a tall tree. A. diminuta and A. gymnanthera have flowers, unripe fruit,
ripening fruit and hard woody fruit - all at the same time (they flower/fruit
continuously) - and Buloke (A. luehmannii) which flowers in about March, takes
about 9 months for fruit to ripen, discharges the seeds around December to
February, and then drops the empty cones.
What this amounts to for the Goonoo Glossies is a
permanent, reliable food source from the shrubby casuarinas, and a seasonal
supplement from the Buloke. (These three species are the only casuarinas
naturally occurring in Goonoo.)
There are continuous stands of River Oak along many
of the watercourses and drainage lines in the central west, and sometimes
"chewings" - ie, crushed cones, are found beneath them. River Oak holds onto its
cones for a long time after ripening to the woody stage and discharging seeds,
but the woody cones will fall off readily, unlike A.diminuta and A.gymnanthera
which keep a firm hold on old cones. Interesting plants, eh?
Back to the birds: What has been bothering me is
that observers who find chewed cones of River Oak might assume that Glossies had
done the chewing...and this could give rise to mistakes in records of preferred
Glossie habitat and presence.
Ahhhh, by the way Carol, re Fairley & Moore's
explanation of the Allo/Casuarina thing - River Oak has dull grey seeds, but
sharp pointy protuberant valves, which makes it...? ( Arrgh! This way
madness lies...) I don't think the CONES are too small for Glossies, but I think
the SEEDS are. River Oak seeds are really tiny, less than 1/2 the size of
A.diminuta seeds which come from a cone of only about 10mm long. Getting at
River Oak seeds would be a lot of energy output for little return.
If anyone does see Glossies feeding on River Oak
I'd be most interested to hear about it.
Thanks again to everyone who has responded to
questions about what my favourite birds like to eat.
Regards, Judie Peet (Dubbo NSW)
(The only thing certain
about bird watching is that nothing's certain!)
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