A living twig

A caterpillar - or a twig
lies on a mix of fallen bark, leaves and branches

While walking through the bush a few days ago, a few kilometers from the centre of Canberra, I found this caterpillar hiding amongst some cast bark at the base of a gum tree - a Scribbly Gum. The caterpillar's camouflage was superb, and it wasn't moving, which would have given it away. But my eye was scouring the leaf and bark litter for spiders, especially peacock spiders which are magnificent if not rather tiny and very tricky to spot. But more of them in a later blog, for now follow this link to read more on them: PeacockSpider

The caterpillar is the one on the right, no the left...

The caterpillar was perched on a fallen branch lying beside fallen bark and twists of twigs which it looked just like. I think it was the distinctive caterpillar shape of a long body, hunched up and ending with two pairs of feet at the rear that attracted my eye. Then once I focused on it, of course it was obvious, yeah that would be right.

I thought it would be a moth caterpillar, and probably of the Geometridae family, and it was. It is a Fallen Bark Looper moth caterpillar Gastrophora henricaria, and it is widespread across south-east Australia. The caterpillars eat gum leaves, up in the canopy during the night, then hide in the ground litter during the day, so that all fits with what I found.

Caterpillars have six true legs as in their adult morph - and they have ten prolegs. The true legs are positioned on the thorax, as in the adults, tight behind the head. The prolegs are spread down the rest of the body and in the Geometridae  three pairs have been atrophied, leaving just two pairs close to the rear. This gap in their leg layout causes them to walk with a looping action, hence the name looper.

A looping motion as it walks and two pairs of prolegs at the very rear - a looper caterpillar

There are quite a few gum trees in the forest I was in, it is several kilometers square, so I wonder how many Fallen Bark Looper moths and their caterpillars there were in the forest - thousands, many thousands - and I only saw one. So, yes they are very well camouflaged animals indeed.

Nest re-cycling

The male Tawny Frogmouth Podargus strigoides sits on the edge of the chough nest

Tawny frogmouths usually build their own nest, a simple platform of twigs and sprigs of greenery, although about one in forty nest records from my study of these birds in Canberra have been in old White-winged Chough Corcorax melanorhamphos nests. These are large, clay nests, which resemble bronze-age beakers set half-way along horizontal branches. In this case about fifteen metres up a Scribbly Gum tree. Frogmouth nests are often flimsy constructions, so perhaps they find these old firm structures as good bases for their nest. They add a few sprigs inside the cup, but don't fill it.

The female sits with the chicks - she has more red on her wings than the male

I have been monitoring the incubation, brooding and feeding rates of frogmouths over the years, studying differences in habitat and weather conditions. Some of this can be done by watching, but it is at times easier and less time-consuming to do this remotely with wildlife-monitoring cameras. So, with the help of Laura Rayner, who did the climbing to this nest, we set this one up, which was about fifteen metres up a gum tree. Once the camera was set and tested, we left the birds for the night and collected the camera the next night. I only approach these birds at night as I do not like to disturb them during the day when they can be vulnerable to predation. They behave so confidently at night, and these birds were feeding their chicks as we were setting up the camera a few metres away.

The chicks, at about two and a half weeks old, were beginning to fill the egg-cup nest

In this case, the adults fed the chicks seventy times overnight, so that was perhaps thirty-five feeds per chick, if they received equal shares. I don't know as I can't identify each chick in all the shots. About half the feeds were in the first two hours after dark, then the feeding rate decreased as the night progressed. And each adult only brooded the chicks for one period of about ten minutes, most of the time the chicks were alone in the nest.

Then as dawn approached the male came in to cover the chicks for the whole of the next day, for it is the male who guards the chicks all day, while the female roosts in a nearby tree. To watch some footage from the camera click here.

A chick peers over the lip of the clay nest

Tawny Frogmouth fledglings

The adult female Tawny Frogmouth Podargus strigoides (left) male (centre) and one fledgling adopt their cryptic pose
- to merge with the branches they are perched upon

The chicks of the earliest breeding tawny frogmouths which I study have just fledged. They left the nest on the night of the 29/30th October and had flown to a tree about 75m away for their first daytime roost. One chick was with the two adults but the other was on its own in a nearby tree.

The male sits over the chick to protect it - all three birds sit in a relaxed posture as there is no threat of danger, it was only me and they probably recognised me, through familiarity, as not a threat

It is usual for each adult to sit close by a chick if they are on separate branches or trees. This one was perhaps not being guarded because it was on a low branch and the adults were a bit cautious to sit so low. Although they were watching over it and would likely have swooped down to protect it if any predator did approach it. All they did when I approached, was lift and turn their heads to watch me intently, as if ready to move if necessary.

One fledgling had landed in an adjacent tree
 - and was not being guarded by an adult, which is unusual

The solitary chick had little to fear however, as it was so well camouflaged against the tree bark and as they do, it sat motionless as I walked past. Most people or predators would not have noticed it.

The fledglings' plumage was still very downy. The main feathers to have developed were their flight feathers on their wings, and the feathers on their backs which would be able to shed any rain and camouflage them against the tree bark. The facial bristle feathers were beginning to take form, hiding their eyes and bill, for now that they have left the nest concealment is essential to their survival as they roost during the day.

Possum twins

The female Common Brushtail Possum Trichosurus vulpecula which lives in our back garden,

 with a single youngster

October is the time for the local brushtail possums in Canberra to be carrying their large young around. We have two females in our garden, shared with our human neighbours, and they both have young. One has the usual single youngster, but the other has twins, which is uncommon. It seems that it is also rare for both young to survive. However, these twins seem to be growing well and it looks like they will both survive.

The neighbouring female in the front garden walking across the drive with her twins on her back

I often go out at night watching for wildlife, and it is noticeable how I have spent hours in the local woods and only seen a few possums in that time. Then when I walk back through the adjacent suburbia, I seem to see a possum in every other garden. This and the set of twins (I have seen possums with twins in the garden before) are signs that there is good feeding to be had for possums around humans. They are one species that is a successful urban survivor.

Doubled up on top

The youngsters have a yellow/orange tinge to their fur which gradually fades to the grey of the adults, as can be seen by the difference in colour between the larger and smaller twins.

The twins are growing fast and putting on weight

The twins can climb already as I have watched them follow their mum as they walked along the branches, but they still take the easy option and travel on their mother's back whenever they can, which is still most of the time. I think that will soon stop.

There is no easy way to climb down a tree with twins on your back

Especially if they make climbing difficult for their mother, for such encumbrance would in  the long run make the whole family vulnerable to predators. So the next stage of evolutionary behaviour will kick in soon and they will have to become more independent. Then we will have three more possums galloping across our roof at night. Mmmmmmm, a bit noisy.

Those prehensile tails can be a nuisance sometimes

Frogmouths incubating

A pair of Tawny Frogmouths Podargus strigoides at their nest site - can you spot them

September is the month when most tawny frogmouths in the Canberra area lay their eggs and begin their four-week incubation. This year, the earliest birds laid on the 26th August and the last ones have yet to lay, which is typical of the spread that I have found in the past several years. I monitor about fifty pairs in my studies of these birds, and they are rather difficult to find as they are well concealed. Yet every time I do find a pair at their nest site I cannot help but admire their adaptation to their habitat.

The male sitting on the nest set in the fork of a tree - tricky to see in the typical dappled light

The male incubates the eggs during the day while the female sits quietly in a nearby tree. Neither will move when approached apart from shifting their posture, usually to an erect stretched pose by which they blend into the shape of a branch. As their colouring also resembles that of a dead branch, they simply disappear into the wood.

The female sits on a dead branch high in an adjacent tree

The dead branch posture is the one most people are familiar with if they come across a bird, but most of the time they sit fluffed up and bask in the sunshine. Some of the birds I study are familiar with me as I have visited them several times a year over the years, they probably recognize me. And it is probably because the birds have seen me so often that they do not go into their branch pose. I have been right next to birds as they have cocked their head right back and opened their feathers to catch the sun. I always prefer to study undisturbed birds so it is especially pleasing to be accepted as not a threat by a wild animal.

A female basking in sunshine, with loose feathers and head tilted to catch the sun

A female adopts the stick-pose, where she resembles a dead branch in colour and shape

As a little footnote, not all the birds build their nests in a branch fork, some use old nests of other birds. And a favourite old nest is that of the white-winged chough. These are mud nests, set half-way along a lateral branch and the frogmouths add just a few sprigs of leaves and twigs to the cup of the mud nest. This might give the birds a more secure nest site than the usual flimsy loose platform balanced in a fork, but they are more obvious to predators. Over the years, I'll gather information on whether the birds that use old chough nests are more or less successful at rearing young than those that use conventional nests.

A Tawny Frogmouth sitting on his nest in an old White-winged chough Corcorax melanorhamphos nest