Cryptically coloured eyes

 When we see a tiger's face close up, unnaturally close - we focus on the pupils but not the irides

During a recent rip to Taronga Zoo in Sydney I was attracted to the eyes of the female Sumatran Tiger Panthera tigris Sumatrae and started thinking why they were that colour. But it is obvious that they are adapted as part of the overall colouring of the animal. As a predator, it would be less successful if, as it crept up on prey slowly easing through the grasses and bushes, there were two bright or bold block-coloured irides staring out from the cover. The prey could detect such eyes more quickly and escape. Eyes sometimes need to be camouflaged as much if not more than the rest of an animal's body.    

When seen from a distance, more naturally - a tiger's eyes blend in with the rest of the animal's cryptic colouring

When I watched the large Saltwater Crocodile Crocodylus prosus in its enclosure, I immediately saw the similar adaptation. In this case the crocodile's eyes are coloured like the greens, yellows and greys reflected on the water surface. What prey species ever saw a floating log with big yellow eyes.

A Saltwater Crocodile swimming with its eyes above the waterline - its irides are coloured like the water

Their first glimpse of a crocodile's eyes would be their last.

Even when seen close up, the eyes are cryptically concealed by their colouring
 - but if you do manage to see a wild one this close, you are too late, it also has big teeth and strong jaws

It's not only predators which have cryptically coloured eyes, some potential prey species have also adapted the strategy, and while still in the zoo I was prompted onto the topic of the obvious arms race between predators and prey. If its works for one, the other can use it too.

It's not only predators that have cryptically coloured eyes,
potential prey species have them too - like this Bush Stone-curlew

The best example I found of a prey species with such an adaptation was the Bush Stone-curlew Burhinus magnirostris. These birds live in open woodland with plenty of leaf and bark litter on the ground. They are largely nocturnal birds, so they lie up on the forest floor during the day - literally so. Their defense strategy is to lie out flat on the litter where their camouflage blends with the dappled greys and browns of the substrate. But they need to keep an eye on any potential predator, so when they open their eyes to watch, their mottled irides do not betray their position.

The Bush Stone-curlew is cryptically coloured all over,
 to match the shadowed leaf-litter habitat it lives in

Zoos might not be everyone's favourite method of saving animals, but in the current world they are necessary. They are educational, as shown here, and they help conserve animals. Taronga Zoo runs various conservation programmes, so if you like tigers and can help financially please click here to help conserve tigers.

Black-eared Cuckoo

A Black-eared Cuckoo has black ear coverts

Following a discussion on the Canberra Ornithologists' Group chatline on the identification of a young Horsfield's Bronze-Cuckoo Chrysococcyx basalis versus a Black-eared Cuckoo Chrysococcyx osculans, I would like to add a few pointers to the plumage differences as described in HANZAB (Handbook of Australian, New Zealand and Antarctic Birds). Unfortunately, I do not have an image of a young Horsfield's Bronze-cuckoo but I refer the reader to the photograph taken by Kym Bradley which opened the discussion on what species and age the bird was that she had photographed. To see the photograph click here to open the page in a new tab for comparison with the photographs taken by me of Black-eared Cuckoos below.

The following text is an abbreviated interpretation of the description on pages 705/6 of HANZAB vol. 4, and I have attached photographs to illustrate the features mentioned, adding further points of note where these are illustrated. The list of pointers described to differentiate between Black-eared Cuckoo (BEC) in all plumages and juvenile Horsfield's Bronze-Cuckoo (HBC) are as numbered in HANZAB.

A Black-eared Cuckoo in 1st year plumage
 - superficially similar to the young Horsfield's Bronze-Cuckoo photographed by Kym Bradley

(1) The BEC is much paler with more uniform upperparts and no conspicuous iridescence or pale scaling to the wing-coverts, as shown above.

Adult Black-eared Cuckoo - showing contrasting pale grey rump against the dark wings and tail. This bird has fresh plumage and as such, because the feathers are not faded by UV light, this bird is a s dark as any BEC is likely to be. 

(2) The BEC has a contrasting pale rump and upper-tail coverts (this is only in adult BEC) as above. The HBC does not have a contrasting rump, nor does a first year BEC. A first year BEC has only a slightly paler rump, see second last image below.

Adult Black-eared Cuckoo - showing buff-cream underparts
and dark chevrons on the under-tail coverts

(3) The BEC has a uniform buff to cream underbody with dark chevrons on the under-tail coverts in an adult, as above, or with no markings in a 1st year birds, as below. The HBC has a mostly white underbody and unmarked under-tail coverts.

First-year Black-eared Cuckoo - showing no barring on under-tail coverts

(4) The patterns on the head are more bold in the BEC; the supercilium is broad and square-ended and the black eye-stripe ends in a broad patch on the ear-coverts, as in an adult shown below. The HBC has a narrower and duller supercilium and eye-stripe.

Adult Black-eared Cuckoo - showing facial markings

A first year BEC has no eye-stripe, but does have a dark patch around the ear-coverts. It also has a pale buff-cream supercilium, lores and throat, as below. The pale colouring of the lores is contiguous with the supercilium, whereas a HBC has dark lores in all plumages.

First-year Black-eared Cuckoo - showing facial markings

(5) The adult BEC has a uniformly dark brown upper tail, with no obvious iridescence (there is s slight glow in the illustration) and a contrasting white tip, as below. The HBC has no white tip, is iridescent and has rufous edges to the base.

Adult Black-eared cuckoo - top side of tail showing white tips

A first-year BEC has pale tips to a dull uniform coloured tail, as below.

1st year Black-eared Cuckoo - showing pale (not white) tips to tail
Also note pale grey rump, but not of high contrast with wing and tail colouring

(6) The underside of an adult BEC's tail also shows a white tip, as below, and lacks the obvious rufous markings on the HBC.

Adult Black-eared Cuckoo - showing underside of tail with white tips,
and dark chevrons on the under-tail coverts

In summary, the bird photographed by Kym has: (1) an obvious iridescence on the wing coverts, which also show distinct scaling on their edges (so it is not a BEC), (3) the underparts are off-white/grey, not buff/cream (so not a BEC) and the under-tail coverts are unmarked (so not an adult BEC), (4) the supercilium and eye-stripe are dull and narrow with tapering ends rather than square-ended near the ear (so not a BEC), and the lores are dark (so not a first year BEC). As rump and tail tips are out of view in Kym's photograph points (2) and (6) cannot be assessed. One further feature of note is the dark grey band across the bird 's throat in Kyms' photograph, this is not mentioned in the HANZAB description (I can't find such anyway) and it does not show in any of the BECs I have photographed, so this could be an additional distinguishing point.

Therefore, in conclusion, the bird photographed by Kym was a juvenile Horsefield's Bronze-Cuckoo.

For further points on Black-eared Cuckoo plumage and age refer to my previous blog posts of November and December 2013.

Superb Fairy-wrens in the garden

The adult male fairy-wren with a woodlouse

A pair of Superb Fairy-wrens Malurus cyaneus have just fledged a brood of chicks from a nest in our garden, outside our bedroom window. The nest was set under an old lavender bush, woven into the mesh of grasses and twigs. It was not much more than a see-through domed cradle for the eggs with the roof for concealment and a thin lining of fine grass and downy plant seed cases to support the eggs and then chicks.

The female creeps towards the nest, ever watchful for predators

The birds were accustomed to me and other people moving about the garden and carried on feeding the chicks while we were close, so I took the opportunity to capture a few images of these stunningly beautiful garden birds.

The large brood of four nestlings begging for food

I spent less than an hour watching the birds feed their youngsters and in that time they made fifteen trips to the nest, the male seven and the female eight times. They brought in a variety of items and I was surprised at the large size of some the prey, the grasshoppers and butterfly being the biggest.

The chicks were about ten days old and well feathered. They all fledged three days later and are now flitting around the garden following their parents in the ever busy search for food.

The male brings in a caterpillar

The female seemed to have the knack at catching flies for she brought in four during the watch.

The female brings in a fly

And she caught a tiny hoverfly.

Then a hoverfly - tricky to catch?

It was such a delightful experience to sit quietly next to the nest while the birds went about their business. Real live wildlife action in the garden. There is no need to travel thousands of miles to see spectacular animals, simply stop and take notice of what is going on all around us, even in the cities, there is something going on somewhere. Who knows what we'll witness next. Just take the chances when they come.

The male brought in two grasshoppers

I thought the male was specialising in the larger items, until the female brought in a blue butterfly, the perfect colour for such superbly blue birds.

A beautiful meal for one of the chicks

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

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

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

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