Monday, 24 November 2014

Hot Frogmouths

The youngest fledgling was on the same branch as its parents
There were some hot days in Canberra during the past week and the birds were feeling the heat. While I was checking on the fledging success of the Tawny Frogmouths in my study, I took a few shots of this family as they know me well and are quite confiding. The adults and the youngest chick were on one dead branch and the other two chicks were up in a nearby tree. The threesome were more discrete, the two others were a bit obvious as their white downy juvenile belly plumage was a bit of a giveaway when seen from below. Fortunately most predators would approach from above, especially Brown Goshawks, so they would be less obvious to them.

The chick was snuggling into its father's shade to escape the beating sunshine
Although the dead branch was a good place to sit for concealment, with their superb cryptic plumage, the open branch was exposed to the sun and the chick there was feeling hot. It was sitting close to its father who shielded it from the direct sunshine. All the birds were fluffing open their feathers and holding their bills open to cool down. This showed off the size of those big wide beaks - rather impressive.

All of the family were gaping wide to cool down - this is mum
The young birds had left the nest a few days before and they could fly quite well, enough to flutter from tree to tree and they were now over a hundred metres from the nest. They would still be dependent on their parents for food though, for another few weeks at least while their feathers fully develop and they gain stronger flight muscles.

The two older fledglings were sitting in a nearby tree - growing feathers are heavy as the quills are full of blood, so this bird is relieving the strain of their weight by drooping a wing
Cool Possum

She was cautious enough in the daylight to only peek out of the box
It was a bit warm yesterday in Canberra, topping at 39 c. And while I was in the garden giving the chickens and wild birds some fresh cool water I heard the possum fidgeting in her box, so I gave the box a quick squirt from the hose to cool it down - it was catching direct sun at the time. Then when I stopped I heard her give a sort of brwuff, a bit like a dog that wants to pay with a stick, not the commonly heard back-throat growl which brush-tailed possums give when disturbed. It sounded like she had liked the water splashing into the box.

She turned her face up into the spray, deliberately catching the water on her face
So, I gave a squirt directly onto the box and she quickly raised her head to the entrance. Whereupon, she happily lifted her head to catch the spray. The camera was handy, so I took a few shots. Then as I didn't want to soak her fur, I stopped, and she gave a me a look which said something. I don't know what, although she seemed to want more. I'm sure her fur is waterproof to a level far above what I gave her, but I left her with that and walked away while she just sat there watching me with a puppy expression.

She looked so calm and relaxed after her shower

Wednesday, 12 November 2014

Tawny Frogmouth fledglings

Three Tawny Frogmouth fledglings gather on one branch
Most of the Tawny Frogmouths in Canberra now have fledged young and I have been out watching them, to count the prey brought to the chicks by the adults. Although they have left the nest they are still very dependent on the adults, as they will be for about a month. This brood of three roosted during the day in separate trees then gathered in one after dusk when the adults began bringing in food.

The adult female brings in food 
The adults fed the chick which begged loudest first, not that their begging calls are loud. This is more of a rough rasping, coughing call, not shrill like that of most diurnal species' chicks. This is probably an adaptation to reduce the risk of attracting nocturnal predators such as owls which can detect prey by listening for such sounds.

The adult male lands with more food - one chick is fed a t a time, while the others watch on
The adults brought in food every few minutes for the fist hour, then gradually reduced this as the fledglings eased off their begging. Slowly they settled down and remained still most of the time apart from occasional wing stretching exercises. I could tell when an adult was approaching with food as the chicks would see them coming before me and begin fidgeting and calling again.

I use flash to photograph the prey which I can identify later at the desk
I watched under the light of the full moon and I could see the adults hunting not far off as my eyes quickly adjusted to the light level. I do not like using torches or spotlights to watch wildlife at night. All one can then see is what is in the beam, we are blind to anything beyond the white. With two weeks of moon larger than a quarter, there are plenty of nights for good watching. I used the flash here to see what prey the adults were bringing in. With flash I can grab an image and identify the prey species later at the desk. And there is no need to use full flash either. I do not like images of nocturnal animals like up like Christmas trees in bright artificial-coloured flash. I like to photograph what I see - softly flying birds in soft light, silent as ghosts (apart from the chicks' spooky low growling).

Mum with two of the kids under a full moon

Saturday, 8 November 2014

White-browed Scrubwren nest

A pair of White-browed Scrubwrens Sericornis frontalis, male behind
A pair of White-browed Scrubwrens nested successfully in our garden this spring and I took a look at the nest once the young had fledged. Two chicks were reared from three eggs, the third did not hatch, as often happens with birds. So all was well and the birds are all still foraging about the garden three weeks later.

The domed nest in situ, hidden at the base of a clump of irises
The birds took over a week to build the nest, the female doing all the work while the male escorted her as she collected material from the garden. She would only go into the nest once there was no danger of predators watching her. Yet she must have made the journey thousands of times.

The nest laid on top of a hat to show the scale of the nest
The nest was large and oval, about the size of a hat crown, with a side entrance well hidden from above by an overhang of grasses. The nest was predominantly made of grasses, including bamboo leaves, and most of the outside was covered with lawn-cuttings mixed with leaves. It looked just like a clump of leaf litter lying in the garden.

The dark interior of the nest betrayed by a single Eastern Rosella feather.  The nest had a well-defined doorstep, seen here laid out to the left of the entrance, and a pronounced overhang above the door which was opened up by the fledglings on the last day when they sat at the door before fledging
Once the outer covering was removed the internal dome could be clearly seen as a separate tightly-knit dome of finer grasses. This was the true nest-chamber, and it felt warm when a finger was placed inside to check the contents.

The inner dome is seen here with the cryptic covering laid open
When opened up, the inner dome was found to be densely lined with feathers and the single unhatched egg
lay there, pale against the dark background. These feathers were wrapped all around the inside of the dome, not only in the nest cup.

The inside of the inner dome was lined with feathers and held a single unhatched egg. The feathers seem pale in the sunlight, but in the complete shaded nest they were dark.
The feathers of the lining were well-flattened into a mat by the large nestlings trampling on them - they were in the nest for two weeks. This and the feather scales in the nest were a sign that the brood had likely fledged successfully.

The fine white feather scales on the nest lining are an indication that the nest held well-grown chicks - for this is the shreds of feather sheaths cast off as the young birds' feathers developed
I then pulled the nest further apart and counted the feathers used in the lining. There 230 feathers; 7 (3%) from Red Wattlebird, 25 (11%) from our backyard chickens, 33 (14%) from Eastern Rosella, 34 (15%) from Crested Pigeon, and the majority 131 (57%) from Australian Magpie. (This might seem like a lot of feathers, but in Europe, the Long-tailed Tit can add 2500 feathers to its nest lining).

Most (222, 97%) of the feathers were dark (dark grey or black) or had a dark base, as with those of the Rosella and Pigeon feathers which were otherwise light-coloured. The few white feathers (8, 3%) were from chickens. Yet there were four white chickens in the flock and only one black, and magpies have light feathers as well as dark ones, so why did the Scrubwrens use so many dark feathers and so few light ones? It might be that the dark background aids the Scrubwrens to see the contrast of their pale eggs and or the light yellow of their nestlings' gapes. Or it might help the adult birds distinguish any cuckoo eggs or young and evict them early. I shall study this further.

All the feathers from the lining laid out

Saturday, 1 November 2014

Tawny Frogmouth Trio

A Tawny Frogmouth flies onto her nest with a large spider to feed to her chicks

During my study of Tawny Frogmouths Podargus strigoides I have collected 342 nest records and most of those have been by pairs of birds. However, four have been by trios of birds, one of which from this year is shown here.

The two females have roosted together all breeding season, about fifty metres from the male on the nest

Two females have been together with a male since the beginning of the nesting season and they are readily identifiable from one another as one bird is grey and the other has much more rufous in her plumage, especially on her wing coverts and scapulars. I didn't know whether these extra birds in breeding groups take part in rearing the young, so I watched this group over a few nights to see if all three birds fed the chicks. Under a quarter moon, there was enough light to see the three birds fly in and feed the chicks and I recorded the incidents with flash photography for confirmation.

The male sits on the nest all day - note his bold markings on a pale grey background plumage colour 

The male was easy to identify as his markings are very bold on his overall light grey body plumage, especially on his breast. At night, under flash, these contrasting markings are even more boldly emphasised. He, like all other male frogmouths which I have recorded at nests, regularly took his turn at feeding the chicks.

The male is readily identifiable by his large size, strongly contrasting plumage and well-speckled breast

When the birds landed with their backs to the camera, they could be identified by the colour of their wing coverts and tail feather patterns. The females were noticeably smaller than the male and they could be seen to bring in prey and feed the chicks which gave soft begging calls as they took the food from the adults.

The red female feeds the chicks 

Here the red female can be seen feeding the chicks, then nine seconds later, the grey female flew in and the red bird took off to the right over the camera. The incoming female can be seen carrying a beetle in her bill.

The red female leaves the nest as the grey female flies in with food

One feature that could only be detected with the photography was the difference in wing feather moult between the two females. The red bird had complete, fully grown primaries, secondaries and tail feathers. The grey bird was moulting three inner primary feathers, with moult scores of 4, 3 and 3, all the rest were complete, more likely old rather than newly-grown as most birds moult post-breeding.

The grey female leaves the nest, showing that her inner primary wing feathers are in moult

These differences in the birds moult were best captured in shots of the birds leaving the nest when they had opened their wings fully on take-off, compared with when they closed their wings on landing.

The red female leaves the nest, showing all primary, secondary wing feathers are fully grown and her tail is complete 

Other data which I collect when watching these birds at night are the frequency at which the chicks are fed, over the whole night, by the different sexes of adult, under various weather conditions etc. It will be a while before I collect all that data though.

Another shot of the red female leaving the nest and showing her complete wing feathering