From Tropical Topics newsletter, No. 73 May
2002, produced by Stella Martin at the Queensland Environmental
Protection Agency. Download the PDF to read the whole issue.
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Golden-shouldered parrot: they use termite
mounds as nests
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Feeding
There is no shortage of food — grass seed — for the
parrots, if the area is not overgrazed. Indeed, for much of the dry
season they only need to feed for a few hours a day, eating the
fallen seed of fire grass, a common annual. They prefer burnt areas
where the lack of cover allows them to find seed on the ground
easily. The rest of the time they perch, safe from predators, in
the trees.
Golden-shouldered parrots were once found throughout Cape York
Peninsula but have been declining in numbers for at least 80 years
and now occur only in two small areas near Musgrave, in the centre
of the peninsula, and to the west of Chillagoe.
Changed fire regimes are considered the main culprit for a
number of reasons. As the fire grass seed germinates with the first
rains of the wet season, sprouting grass obscures seeds still lying
on the ground. However, if this new growth is burned, ungerminated
seeds which remain become visible to the parrots. Fires at this
time seem to be vital for the parrots’ survival, allowing
them access to seed which will keep them going until the perennial
cockatoo grass produces seeds about six weeks later. To complicate
matters, cockatoo grass which is burned after the first storms
produces up to 10 times more seed, later in the season, than the
unburnt cockatoo grass. Evidently, a complex mosaic of small areas
burned at different times is most likely to provide a sustained
source of food for the birds. Early wet-season burns are
particularly important, but if extensive dry season fires have
already used up the fuel, they may not be possible.
Another aspect is the trend for grasslands to be
invaded by woodland, particularly broad-leaved ti-trees
(Melaleuca viridiflora) where fires are infrequent. These
trees have a tendency to sucker from the base. Frequent fires will
keep the suckers below grass level but once the trees have had a
long enough fire-free period to grow over a metre in height, only
very hot fires will kill them. The presence of these trees affect
the parrots in two main ways. Dense growth cuts out light, thereby
reducing grass growth and food resources. They also provide nesting
and perching sites for butcherbirds which are major predators of
both young and mature birds.
Woodswallows stand guard
At first glance, it seems unlikely that seed-eating
parrots and finches would have anything in common with
insect-capturing woodswallows. However, researchers have noticed
that golden-shouldered parrots and hooded parrots, (similar parrots
found in southern and eastern Arnhem Land, Northern Territory) are
often to be found feeding on the ground below black-faced
woodswallows during the woodswallow nesting season from the late
dry to early wet seasons.
Finches too join in — Gouldians, long-tailed and masked
finches alongside the hooded parrots in the Northern Territory with
blackfaced and masked finches joining the golden-shouldered parrots
on Cape York Peninsula. Even doves, trillers, sittellas, willie
wagtails, leaden flycatchers and treecreepers have been observed
joining the party.
It seems that the woodswallows act as sentinels. When a predator
such as a butcherbird or kookaburra comes anywhere near their
nests, these feisty birds mob and chase them. This serves as a
warning to birds which have their heads down, intent on finding
seeds on the ground. It allows them to spend more time on feeding
and less on looking around for danger. Given that butcherbirds prey
not only on eggs and nestlings but also on adult, breeding parrots,
the woodswallows offer a very valuable alarm service.
Whether they are repaid for this is not clear. Possibly the
seed-eaters disturb a useful number of insects as they forage. Once
the woodswallows have finished nesting, however, the other birds
lose their alarm system, unfortunately at a time when food takes
longer to find and entails a longer period spent, vulnerable, on
the ground.
Curiously, one group of golden-shouldered parrots formed an
association with grey-crowned babblers, relying on their alarm
calls.
