Thursday 5 November 2015

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




Sunday 1 November 2015

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.



Wednesday 14 October 2015

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


Wednesday 30 September 2015

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

Monday 28 September 2015

Dry woodland orchids continued.....

Wax Lip Orchid Glossodia major
There seem to be more and more orchids coming into bloom every day at the moment in the Canberra woodlands. Today the forest floor was peppered with blue dots of wax lip orchids in numerous colonies. The blue of these flowers is so intense, and really emphasised, by the the grey leaf and bark litter that they grow amongst. Although they are not as obvious as would seem as the strong sunshine bounces off the ground cover, making it difficult for human eyes to discern the colours in the brightness.

Dry woodland orchid habitat in Canberra 
Also, the orchids are only about 20cm tall, shorter than the grasses, but as one walks through the grass, the flowers appear into view on looking down into the sward. One after another.

A cluster of three Wax Lip Orchids - two still in bud
The most I saw in any one cluster was perhaps seven or eight, but the clusters are only part of larger colonies of twenty, forty, or more flower spikes. Then there will be a gap of a few hundred metres before another colony appears out of the grass.

A typical view looking down on these forest-floor orchids
The other orchid species I saw today, but not previously this year, was the brown caps. There were fewer of them showing and being white, they were probably less noticeable. All the more rewarding to see.

Brown Caps Orchid Caledenia ustuluta
This group were growing on the top of a gully bank, between low-lying shrubs and if not in flower they would be difficult to pick out from the foliage.

Profile of a Brown Caps Orchid flower
The detailed structure of orchid flowers are famous, and bewildering in their variety, with each feature having evolved for a reason to help the species cross-fertilize. They are fascinating when viewed up close, singly or in multiple flower-heads on one stem. No wonder they have so many human admirers.

A stem of Brown Caps Orchids with four flower heads