It was a sultry night, especially for March. Tiny flying insects kept landing on my laptop’s screen, attracted to its light as I sorted through the day’s photos. I’d settled into my cabin for the night on an isolated bush property in the Capertee Valley. The rocky escarpment rising steeply behind formed an imposing presence, even in the darkness of a moonless night.
The quiet was punctuated by the short, shrill churrs of an Owlet-nightjar. The Zebra Finches had gone quiet, asleep under the verandah roof where they regularly build nests in the corners of the metal rafters. Although popular around the world as cage birds, these are wild Zebra Finches on their native land. At times down in the paddocks you can see flocks of dozens to hundreds feeding on grass seeds and drinking at the farm dams dotted around the landscape.
The cabin verandah provided a nice sheltered site for their nest. Despite the occasional disturbance from torchlight and human activity it was safely out of the reach of predators…or so it seemed.
All of a sudden there was a thud and the sound of something sliding noisily on the steel roof. I’m still not sure exactly what was happening at that point but it caused me to stop what I was doing and look outside. Just then the female Zebra Finch landed on the screen door, clinging to the wire in fright. I shone the torch around the verandah and she took flight again, crashing into the roof and windows in a state of panic. Out the corner of my eye I glimpsed a second bird flying away, I think her mate.
Then I saw the cause of the disturbance. A snake, richly coloured orange-brown with dark flecks forming an irregular banded pattern on its body, was stretched along the rafter with its head inside their nest. A Brown Tree Snake, Boiga irregularis, at least a metre long.
My heart skipped a beat as the panicked female almost landed on top of the snake, thought better of it and eventually flew off into the darkness.
The snake was in no hurry. I grabbed my camera. After I snapped a few photos it slowly lifted its head with something in its mouth. At that point, with my binoculars out in the car, my camera played up and refused to focus. Why do these things happen at the worst moments? The snake slowly doubled back and moved along the rafter to another nest in the next corner. Finding nothing inside that one it continued on its stealthy way under the roof. By this time my camera had regained its focus.
The Brown Tree Snake is aggressive and mildly venomous but, with fangs at the rear of the mouth, not considered dangerous to adult humans. But for birds, frogs, lizards and small mammals it can be a nightmare prospect. This is well illustrated by the story of their introduction to the Pacific island of Guam.
At the end of the Second World War the species was accidentally introduced to Guam where, with an abundance of prey and no natural predators it quickly became established and thrived. In a short time it had a devastating effect on the birdlife, wiping out 10 of the island’s 12 forest bird species.
Although native to eastern and northern Australia, New Guinea and eastern Indonesia, it was a surprise to see one here in the NSW Capertee Valley. They’re uncommon this far south with Sydney close to their southern limit, and there are scattered records in the Blue Mountains and Wollemi National Parks. I wasn’t aware of any previous sightings in the Capertee, but since posting a photo on Twitter I’ve learnt of one other sighting in the valley, a recent roadkilled individual.
So has it always been lurking around the valley in low numbers or is its range expanding? A couple of people have suggested it might have arrived as a stowaway, though it is on the edge of its natural range. While I can’t answer these questions, I’ll certainly be watching out for it in future — with a little apprehension. The Capertee Valley is renowned as a bird-rich area and home to more than 20 threatened species, including the critically endangered Regent Honeyeater.
I don’t know if there were eggs or chicks in the finches’ nest but the snake obviously got a feed of something. Zebra Finches are prolific breeders and can lay at any time of year in suitable conditions. They weave their rounded dome nest of dry grasses and line it inside with collected feathers. The rufous feather that clung to the snake’s mouth as it slid away was not a Zebra Finch feather but no doubt part of the nest lining.
The next night there was no sign of the snake or the finches. Frankly, I don’t blame the zebs for finding somewhere else to sleep.