Black faced woodswallows. © Mike Gillam.
By MIKE GILLAM
Updated 14 July 2020 3.03pm. Minor corrections.
Black faced woodswallows are huddled together trying to stay warm, photographed from my kitchen window. This family group found an agreeable winter perch on the lee side of the house which blocked out the very fresh south-easterlies and allowed them to bask in the weak morning sun streaming through a gap in the trees. The day was overcast and warmth precious.
In Arrernte the woodswallows are called rlperrpaye or iperrpaye. They frequently roost together for warmth and protection in both family groups and larger colonies. Flock members (possibly related) are also known to assist breeding pairs to feed their young.
The woodswallows are genetically similar to butcherbirds, Australian Magpie and currawongs. On the Cape York Peninsula, the Black-faced woodswallows associate with Golden-shouldered parrots and finches, which has important consequences for the endangered parrots. In the Northern Territory similar observations have been made for woodswallows and the endangered Hooded parrot, with the parrots using the woodswallows as sentinels to warn of the approach of potential predators.
Abundant and widespread in Centralia Black-faced and masked woodswallows favour open lowland sclerophyll woodland, and rich inter-zones of Eucalypt, ironwood and mulga grasslands where a mosaic of plant communities produce huge volumes of flying insects.
These aerial predators are often seen at dusk in large flocks, numbering in the hundreds. This behaviour may be important for social bonding, a joyous salute to the setting sun perhaps but more likely the flock is hoovering insects, a flying host that is often too small for us to see.
Certainly I’ve watched these slowly rotating flocks gradually moving over groves of mulga and then reaching a dam, pause in a holding pattern for a good ten minutes. During this timespan they reduced altitude from a height of roughly 80 metres to less than half that before gradually and effortlessly returning to their original height and moving on.
The flock seemed to expend little energy in their aerial manoeuvres, a mesmerising rotation of smaller flocks and possibly family groups within the greater order.
I lay on my back and tried to work out what the birds were doing. It was confusing to me and that feature probably offers members of the flock some benefit against predators. I took a few images and zoomed in so I could identify the species.
Most if not all were masked woodswallows and there was a handful of zebra finches and even a solitary budgerigar enjoying the experience. It was a long time ago but I seem to remember elements within the flock were gliding/flying both clockwise and anti clockwise; the flock appeared as a giant organism working cooperatively for some higher purpose.
I turned my head and looked across the water at the rising plumes of backlit mosquitos. Maybe.
Bloodwood. © Mike Gillam.
The sun was setting, the orange blush of day giving way to the blue black of dusk. To the north-west a late season electrical storm lit up the sky over the Tanami Desert. I know what it’s like to be in the middle of such a storm cell, sharing your bedroom with a Toyota four wheel drive, the tallest element in a flat landscape and all that steel!
The storm was suitably violent, impressive and safe at that distance, the sound of thunder, muffled. As the leading edge of the storm moved closer, the wind picked up.
Crossing the open Mitchell grass plains and spinifex hummocks of Amburla a strengthening wind entered the labyrinthine woodlands of whispering mulga. The wind’s raw energy and direction was flagged by the thrashing tops of infrequent ghost gums and bloodwoods that rise above the stands of dense mulga.
At ground level the witchetty bush, yellow flowering Sennas and chenopods in paler shades of cyan moved imperceptibly, a barely audible rustle.
Where the mulga was replaced by an open woodland mosaic I sat watching a large bloodwood dancing in the fading light, its fearsome visage softened by the twirling and shaking of bunched leaves, held like batons to catch the breeze. I thought of Indigenous dancers with leafy bunches encircling upper arms and ankles, brought to life by stamping feet.
A small group of budgerigars settled on a bloodwood branch, choosing the lee side and the protection it gave from the wind gusts whipped up by the storm’s leading edge. With the grim determination of sailors clinging to a ship’s mast, the budgerigars pressed bodies against the branch, dug their claws into wood and braced.
In the low light the bloodwood galls of which there were many, some the size of oranges, appeared as macabre trophies, a warning to some, a comfort to the hungry and a sign of the teeming invertebrate life that exists here.
I knew a torch shone up into the deepening sky would likely reveal a swirling soup of pollen grains, wasps, thrips, aphids and moths and after rain huge numbers of ant and termite alates. A most productive woodland in every sense and yet for some, a place begging for bulldozers and chains.
There would be ballooning spiders of course, carried and propelled by threads of silk and lifted from the tops of branches by the earth’s electric field. Now I heard the bats and the first stars appeared. I imagined geckos peeping out, watching me from the cavernous maw of the bloodwood mask.
Pygmy goanna, Varanus tristis. © Mike Gillam. (Roofing nail shows scale.)
It was time to return home where the hungry urban geckos gathered on window panes, ever hopeful in a season of scarcity. The next day I would return before sunrise, in time to see the dew sparkling on a spider web village, adding yet another layer to the sculptural pattern of zebra finch nests crammed into hardy Acacias.
Each year the pygmy goannas take their toll on the egg clutches and nestlings of woodland birds including zebra finches and wood swallows. The goannas live in tree hollows and beneath the flaking insulated mulga bark which they share with geckos, centipedes, bizarrely flattened spiders, king crickets and numerous smaller invertebrates.
Regretfully I should mention the aggregation of fabulous but squashed jewel beetles I once saw in the back of a wood cutter’s utility stacked with mulga firewood.
In this confined domain, the anatomically flattened inhabitants move between shallow caverns where the bark has cupped and buckled outwards and intervening squeeze spaces where it’s still attached to the trunk.
Throughout the day ectothermic reptiles are able to thermo-regulate by switching between the sunny and shady sides of the tree trunk. Vertically they can move unseen into the upper reaches of the tree to a place that provides a perfect lookout for a juicy centipede or a skink moving about at ground level.
Hour after hour the goanna waits, hidden from falcons and kites and predatory corvids, with just its head exposed. Finally, the goanna launching itself to the ground, belly flops and chases down its prey.
With the early winter frosts, many reptiles become dormant, larger species may be inactive for several months whereas smaller lizards may interrupt their slumber on the warmest winter days and briefly try their luck at hunting.
Two species of pygmy goannas inhabit this open woodland and the dense stands of mulga. They are fearsome predators and adept climbers. One, Varanus gilleni is vey closely associated with mulga and so more restricted in its distribution.
The other, Varanus tristis, occurs more widely and is reasonably abundant in urban areas where it’s a predator without equal, of the introduced house mouse, Mus musculus.
For a time during my employment with the Conservation Commission I was responsible for displaced, injured, orphaned and dangerous animals in the town area. This role brought me into contact with some of the most empathetic and generous people in the world and also a few, less so. By and large, most people were open to advice and simply wanted to do the right thing.
“Hello, there’s an animal scratching around in the roof of our house, I think it must be a possum, can you come and get it out?”
“Sure I’ll take a look but it’s definitely not a possum. Wish it was.”
A layer of desert dust showed the foot prints and tail scrape on the upper side plasterboard ceilings.
“Here’s the thing. I’ve looked in the ceiling space and the tracks confirm a small pygmy goanna is living in your roof. It moves in and out through the gaps in the eaves and it can’t get into your house. I could trap it but come winter you’re going to hate me when the place is over-run with vermin.”
“Yes, European house mice breed very quickly and they will definitely invade your house in the dozens.”
“So what are you saying?”
“Well, if I could bottle this goanna with a fancy label people would be lining up to buy them. This is the ultimate mousing machine, better than any cat. You should really have a permit to keep it.
“So I suggest you might be grateful for this good luck and whatever you do, don’t use mouse baits because that’s one way of destroying your best friend. If the goanna misses a few mice, then you should use traps and help it out. Make sure you tell your neighbours.”
I’m pleased to report that no-one, even those with a misplaced fear of reptiles, ever insisted that I remove the scratching goanna, a small victory.
In our neck of the woods in Hele Crescent we never use mouse baits, a sure way of killing non-target wildlife, including owls and goannas that might eat sick and poisoned mice. Thanks to the healthy population of small varanids, our local form of biological control, we’ve never had a problem with house mice.
We see the goannas often, sunning themselves on external brick walls and occasionally we hear one thunder across the ceiling followed by the squeal of a dying mouse.