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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

Thursday, 30 October 2014

Sun Orchids

Trim Sun Orchid Thalymitra peniculata 

The current warm and sunny Spring seems to be suiting the local orchids as there are thousands of them in flower in the woodlands around Canberra at the moment. The shy Sun Orchids are the species that I have particularly noticed this year on Black Mountain. This is a great place for orchids in number and variety with about sixty orchid species recorded in the woodlands there. I don't go out looking for them especially, I simply notice them while in the woods looking for Tawny Frogmouths, my main study species here in Australia.

Trim Sun Orchid in woodland habitat

Some orchids grow in small colonies, however the Sun Orchids are usually found singly and as they are slow to open their flowers every day, and only if the sun is bright, they can be easily missed. The tallest of these plants was the Trim Sun Orchid which stood erect at about 40cm, which was just about the same as the surrounding grasses so it was well concealed until it opened up and displayed its bright purple-blue petals.

Large-spotted Sun Orchid Thelymitra juncifolia

The most difficult to find species of those shown here was the Large-spotted Sun Orchid as they were growing in partially shadowed woodland, where the dappled light hid them in the partial shadows - always tricky conditions for our eyes to detect anything due to the loss of detail in the contrasting light.

Large-spotted Sun Orchid on forest floor

The one species I found out in the open grassland on the edge of the forest was the Slender Sun Orchid, the smallest of those here with a flower only 15mm wide. They were growing in quite tight flower spikes and reminded me in their form and soft hue of alpine gentian species.

Slender Sun Orchid Thelymitra pauciflora 

I might have found these orchids difficult to find but the local herbivores seemed to find them alright. There are Eastern Grey Kangaroos, Swamp wallabies and  rabbits all in there munching away. When I passed through the area a few days later, the flowers were gone, the plants were gone. So they weren't just not open or gone to form seed and even more tricky to find, they had been eaten. What a beautiful meal.

Slender Sun Orchid plant in grassland

I thank Dennis Wilson for help with identifying these orchids, he is always so patient with me.

Saturday, 25 October 2014

Noisy Miners

Two Noisy Miners - a pest or a successful adaptable species?
As a woodland species that favours clear ground with not much shrubbery, Noisy Miners Manorina melanocephala have adapted well to the human-cleared woodlands around Canberra. They nest in loose colonies with their nests about a hundred metres apart, and as they as very demonstrative against intruders they fit their name. Although we can tolerate their mobbing and chasing, smaller birds can't and many parts of the woods which hold Noisy Miners lack some of the usually more common bird species.

A typical clutch of three Noisy Miner eggs lying on a lining of kangaroo hair
A secondary factor which also helps the miners dominate parts the woodland is the grazing of the understorey and grasses by Eastern Grey Kangaroos Macropus giganteus. These large herbivores have grazed the ground cover down to very short swards and bare ground in some places. And in the absence of a predator, the kangaroos numbers are abnormally high. The local authorities do cull some animals but the population was allowed to build up to such a high level previous to this that it will take many years before the vegetation is restored to a more balanced composition of ground cover and shrubbery, which in turn will support a wider range of animal life including those missing species of birds.

But the Noisy Miners are happy and they further benefit from the kangaroos by using their cast fur as a lining for their nests. So, can these two species be regarded as pest native species, due to their abundance and effect on the woodlands and other bird species, or are they simply successful adaptable species that can thrive in a human-created landscape.

A group of Eastern Grey Kangaroos in Canberra woodland with little understorey