Thursday, 26 September 2013

Buff-rumped Thornbill nest

A well hidden thornbill nest
The woods are busy with the sound of nesting birds at the moment. Some building, carrying material, some scolding in alarm as we pass by and others make almost constant contact calls between one another as they gather food for chicks. Chicks which lie still in hidden nests, but can blow their cover by emitting urgent begging calls as they see or hear their parents approach with food.

This nest is of a pair of Buff-rumped Thornbills  Acanthiza reguloides. It is a neatly crafted ball of bark strips and grasses locked together with spider webs and egg cases, then lined with what looked like a mix of small feathers, kangaroo hair and plant down. Set in a crack behind some flaking bark on an old Yellow Box tree it was invisible from most angles, except from that from where the side entrance could be discerned as a tell-tale round hole in an otherwise linear pattern of bark. 

I heard the adult birds first, calling to one another, then they gave alarm as I approached their nest tree. I could see they were carrying food; a large moth in the first case, the other something very small, so I walked back a few paces and watched the birds sneak into their nest to feed their chicks (3). They quickly set off for another foraging trip, and I knew I had about two minutes before they returned. So I unzipped the camera as I approached the tree, found the nest straight away, took a few shots, and walked away before the birds returned. Minimal disturbance, means minimal risk of predation by ravens or currawongs.

Small birds only need small niches to nest in - some very small
One Frogmouth less

The scattered feathers of a plucked Tawny Frogmouth
Today, while checking what used to be a Tawny Frogmouth territory, looking for this year's nest, I couldn't find anything. No nest, no birds. Then I found out why. There was a cluster of plucked feathers, from a Tawny Frogmouth, lying not far from the previous year's nest site. As the quills were all pulled out rather than snapped off, this is indicative of the bird having been killed and eaten by a raptor, most likely a Brown Goshawk as they nest a few hundred metres from the site. A mammal would have bitten off the feathers leaving cut shafts.

The kill was not recent, and as I could not find even a partially-built nest, I reckoned that the bird had been killed before the pair had began nesting. I still could not find the other bird of the pair, but it might have shifted a few hundred metres, and perhaps found a new mate and still be breeding. That will take another visit to check.

The complete shafts indicate that the feathers were plucked by a raptor.

Wednesday, 25 September 2013

Tree-creeper bill shape

Adult male White-throated Treecreeper
One of the advantages of mist-netting birds for banding is the opportunity to see them as we seldom have a chance to do so when they are flitting about the woodlands or wherever they live. While we were banding, aging, sexing and measuring this White-throated Treecreeper Cormobates leucophaeus during the same study as the previous blog article below, I noticed just how fine its bill was. There is a graceful curve when seen side on, but when viewed face-on, the bill can be seen to be remarkably tapered to a point. This is an adaptation for probing into cracks in tree bark, where they hunt for their food; tiny invertebrates.

The sleek lines of the treecreeper's bill - superbly adapted for reaching and grabbing tiny insects under bark
In comparison, other birds we caught that day included the Western Gerygone Gerygone fusca with a fine pencil-pointed bill for feeding on the tiniest of insects. Very fine, but straight and simple in line as it has no need for any further specialist shape like the treecreeper.

The tip of  this Western Gerygone's bill is polished by contact with the surfaces it has lifted insects from
There were also honeyeaters, which have slightly curved bills for probing into flower-heads to sup nectar, but their bills are mostly sturdy like that of this White-plumed Honeyeater Lichenostomus penicillatus as they also eat insects. The bill is very much thicker than that of the treecreeper.

The White-plumed Honeyeater has a slightly curved bill for accessing nectar in flower heads
And we caught a the generalist insect-eating Rufous Whistler Pachycephala rufiventris.  It has a broad, thick bill with a curved tip on the upper mandible, which enables it to catch insects on the ground or in the air and hold them firmly. Only when we held these birds successively in the hand did I appreciate just how finely tuned the treecreeper's bill is. Evolution is marvelous. 

An adult female Rufous Whistler: the hooked tip to its bill helps it hold prey tight

Monday, 23 September 2013

Breeding season feathers

Adult Laughing Kookaburra
I was out helping Mark Clayton with several others at a cooperative bird-banding site over the weekend, out by West Wyalong in New South Wales. The season is warming up now and there was a heavy fall of rain several days prior to our visit. Many of the birds were breeding, and I noted how we were catching more male than female birds, probably because the females were doing more incubating.

It was also a good chance to see adult birds in full breeding plumage. Although, as most of them had moulted into that plumage months ago, some of their flight feathers were beginning to look a bit tatty. This Laughing Kookaburra Dacelo novaeguineae, was an adult, although it could not be sexed because it did not have a large blue patch on its back like a primary male would have. As it only had a small blue patch, too small to even see in these photographs, it could have been either an adult female, a young female or a secondary male. Kookaburras are cooperative breeders, and the males also incubate the eggs, so even the presence of a brood patch was no help in sexing this bird.

The bird had a well developed brood patch: a large patch of bare loose skin, with a rich vascular supply

It was still early in the breeding season, so the birds had not yet begun to moult. They all had full sets of old flight feathers on their wings and tails.

A full set of flight feathers
Some of these feathers were beginning to fray at the tips, through wear and tear as the birds go about their business, flying through branches and catching their tails on the ground. The central tail feathers are particularly prone to wear as they project farthest and take most of the abrasion, so they are usually the first to show signs of age. Most of these birds will begin to moult out these battered feathers and grow replacements as the breeding season progresses.

The pair of central tail feathers on this kookaburra's tail are well frayed.

Thursday, 19 September 2013

Sugar Glider

A tree came crashing down today
While I was out looking for Tawny Frogmouths today I heard a crash and looked around to see an old tree fall down. I thought it might be interesting to see what animals had been disturbed, or lost their home as I could see that the tree was very old and had some cosy holes for animals to sleep up in.

Sue enough, as I approached, a Sugar Glider  Petaurus breviceps slipped out of a broken branch and scuttled up the nearest standing tree. It wasn't too alarmed by my presence, but did go high up very quickly. For that is their strategy to escape, they can climb well, but they can fly too. And when it reached the highest branches it simply jumped into space and glided onto the next tree about twenty metres away. It landed on the top of another dead tree which it clambered down until it found a hole it could wriggle into. And that was that, a new home, safe from predators.

The Sugar Glider dashes up a tree

Once up high, the glider stopped to watch me. The folds of skin which help it glide can be seen rippled along its flanks.
Meanwhile, take a look back at the first picture. There are a pair of frogmouths up in the tree, in the top left. I noticed the male's tail protruding out from the nest after the glider had disappeared and I could re-focus my attention to my original purpose. 

The male frogmouth is on the left, on the nest, his partner is on the branch above

Tuesday, 10 September 2013

Tawny Frogmouths at night

The moon and Venus above the female frogmouth
I was out watching the frogmouths last night with Steph and Matt. There were a pair which appeared with fledged chicks last year from an unknown nest site, so we staked out the area at dusk. The female was calling from her daytime roost perch for ten-fifteen minutes as the light faded. Then as it became truly dark she shifted to another perch and continued to call her rapid repeating 'ooom-ooom'. The call is distinctive, but so soft, we wondered how far away her mate was. The call only carried to our ears for about fifty metres. Do they do so to avoid attracting attention from their main night-time predator, the Powerful Owl? Then the male swooped in silently from the shadows and landed right next to her. She twitched her tail, he jumped onto her back and they mated for a minute or so. He then went off and hunted, catching an insect from some foliage up in a tree. She flew over to their nest site and continued to call. 

So, we accomplished our quest to find the nest site and all this happened in about half an hour immediately at the onset of true darkness. There is so much to see in the dark.

The distinctive silhouette of a Tawny Frogmouth - a broad, bushy head and a tapering tail 

Monday, 9 September 2013

Bearded Dragon

Flat out
The days are warming up and the first of the larger reptiles have been out and about. The Shinglebacks Trachydosaurus rugosus are wandering slowly about the bush and others like this Bearded Dragon Pogona barbata are spending much of the days warming themselves up in the sunshine. This one was well camouflaged with its dusty skin matching the open dirt between the grass tussocks. It lay motionless as I stepped past it; its legs hung down along its tail, its skin spread out and the whole body aligned with the sun, all to maximise capture of the radiant heat.

It seemed to be trading off the powers of its concealment against the expenditure of its limited energy, having just warmed up a little and not being very active yet. For it was keeping a steady eye on me in case I did after all pose a threat and it would have to use that little energy to flee.

An eye watches through the camouflage