Bird Pollination

An adult male Eastern Spinebill sitting on a grevillea bush outside my study window

I've been at the desk a bit too much recently, but it is has turned out quite entertaining as our garden in Canberra is busy with birds - and they have been a great distraction. Right outside the window, about a metre from me as I type, there is a small flock of Eastern Spinebills Acanthorhynchus tenuirostris feeding on a flowering grevillea. Spinebills are a species of honeyeater, and like their name suggests, they specialize in feeding on nectar, which grevilleas produce in abundance.

An adult spinebill dips its bill into a grevillea flower for nectar

An immature spinebill dips its bill into the same grevillea flower.
These birds are about sparrow size.

Grevilleas are part of the protea family and they have a highly adapted form of flower. The inflorescences - the flower spikes - have multiple flower heads held in tight clusters and with over three hundred species, they come in lots of shapes and sizes. They have evolved to be pollinated by different species of birds, insects or small marsupials, such as sugar gliders, but especially honeyeaters. There are over 60 species of honeyeater, mostly in Australia and the two families have similar geographic spreads in the general Australia/Oceania area. So, the honeyeaters are probably the main pollinators.

A Spinebill hovers to feed from a pendulous inflorescence.
Honeyeaters have evolved to feed on nectar like hummingbirds, but they are not so well adapted for hovering flight. However, they can also creep through the branches and feed safely under cover away from predators, and  humming birds can't do that, or do they need to?

Grevillea flowers have an exaggeratedly long style which unfolds with a sticky pad of pollen grains around the stigma at the tip, the pollen-presenter. The pollen is transferred from the anthers to the style as the flower opens and there are some unfolded styles in the first two photographs above, they are the curling loops above the petals. The nectar sac is cunningly concealed between fused petals and can only be reached via a slim opening. An opening which the spinebills can probe into with their fine long, curved bills, but many other animals can't gain access - this pollination strategy is selective towards species that can transfer the pollen. As the birds dip their bill into the nectar, they touch the pollen-presenters and a deposit of sticky pollen is left on their crown. Then, when the birds fly to another grevillea plant, they brush against another flower's pollen-presenter and the pollen is passed onto the style and into the stigma. And that's it, all done, the flower has been pollinated.

A Spinebill is dabbed on the head by a pollen-presenter as it feeds from a flower.
This bird is a juvenile, recognised by the fold of yellow skin at the base of its bill, the gape, which is a leftover feature of a fledgling. It will soon lose this, and the base of its bill will darken too as it grows into adult plumage during its first year of life.

Pollen sticks to the crown of this spinebill's head as it dips between a crowd of pollen-presenters

Spinebills, like other honeyeaters which are specialized nectar-feeders, have brush-tipped tongues, an adaptation that allows the birds to lap up the nectar from the tight space inside the nectar sac.They don't gain much per flower-visit, so these birds are busy when feeding, and they are busiest in the morning and late afternoon. Which is fine by me as I see them first thing and then at the end of a long desk session, without too much distraction during the middle of the day.

The tip of this spinebill's tongue can be seen as the white part protruding from the end of the bill - it's very delicate

Sawfly larvae

The Old Weetangera Road - horse-drawn carts and coaches used to drive along here. 

Autumn is well and truly here now in Canberra, making great mornings to be out in the bush, and on the weekend I went for a walk along the old Weetangera Road through the Aranda Bushland Nature Reserve. The birds are now in their winter flocks, with roving packs of Pied currawongs ranging through the canopy searching for insects, and the various passerines were in mixed-species flocks, rolling and weaving through the shrubs and lower branches.

A ball of Sawfly larvae hang onto the stem of a eucalyptus sapling - follow the arrow

How the birds spot and catch insects so quickly is always fascinating to watch, but one insect that few birds can tackle are sawfly larvae. I noticed a ball of these lying up for the day on a sapling gum tree. These are a species of Perga sawfly larvae, they spend all day huddled together for protection, then a leader of the pack leads them to forage out on the eucalypt leaves at night. Like all sawflies, these are hymenoptera and related to bees, wasps and ants.

A knot of Sawfly larvae lie up for the day
- they seem to lie head to tail, probably for cautious defence -protected at both ends

Another defense strategy they use is to release a nasty fluid from their mouths, based on eucalypt oils. Although they are called spitfires for doing this, they don't actually spit the fluid, it just sort of oozes out. The tactic is effective though and few animals bother them. Except, for example cockatoos, the local Gang-gang Cockatoos will pick one at a time out of the bunch, chew them, lick out the juicy contents and spit out the spiny skins.

They use their pointed tails to tap on branches,
a simple means of communication to keep the group together when feeding

To read more on these amazing insects click here to access the Victoria Museum website.

Possum Raids Figs

The Brush-tailed Possum caught raiding the fig tree

After the success of catching the cockatoo raiding the chickens' food bins last week, I thought I should try to find out who was raiding the figs and focus a camera-trap on the fig tree.

The figs are the last fruit to ripen in our Canberra garden at the end of summer and we always look forward to opening a nice ripe one for breakfast. But, not this year, some animal has been eating them before we can pick them.

At first I thought it might have been fruit bats as I have seen them on the tree in previous years. Not this time though, the thief was a Brush-tailed Possum. It was a female, probably the one that sleeps in one of our garden nest-boxes, although if it was her, she has parted with her joey. The last time I saw her a week or so ago, she had a large joey (a young marsupial) in tow, still trying to hitch a ride on her back even when it was at least half mum's size.

She will probably have a new tiny joey in her pouch already, so I suppose she will want to add a hint of fig flavour to her milk. Lucky possums.

To watch a clip of the surveillance film, as evidence of the criminal's identity, click here.

We do like the possums, but...... there are times......

Scribbly Gums

A rich mix of old and young trees in Black Mountain forest

I have noticed that there have been many more features on wildlife than wildpaces lately in the blog, so I shall try to adjust this. First off, this gave a reason to go for a walk in one of the local forests, the 500 ha Black Mountain Nature Reserve, which is only two kilometres from Canberra city centre  The woodland is dominated by two eucalyptus tree species, Scribbly Gum Eucalyptus rossi and Red Stringybark E. macrorhyncha, and the under story is mostly a sparse covering of grasses and short shrubs. The trees provide thousands of cavities for such animals as possums and parrots - especially Crimson Rosellas, while I often see swamp wallabies and echidnas working through the undergrowth.

Wild forest in the foreground - urban high-rise only a mile away

There are numerous tracks to follow through the forest and multiple variations of routes to take. On today's walk I went around the summit and looked down onto the city. And I noticed how, even the city looked green with the street and park trees shining between the buildings.

A zoomed-in view of Canberra city from Black Mountain

Now that it is late summer, some species of eucalypt trees have shed their outer layers of old bark to reveal shiny new skin. The Scribbly Gums do this but not the stringybarks.

This fine old Scribbly Gum has large and small hollows,
 it is a true veteran, yet is still throwing up young branches from its old trunk.

The cast bark lies thick on the ground in some places, giving homes and shelter to all sorts of animals, but it can build up deep enough to become a fire hazard and Canberra, as the bush capital, is well aware of the danger of bush fires. So there are regular burn-offs of the ground cover over the years to prevent such a risk.

Shards of bark lie about the base of the gum trees, their inner surface glowing red in the sunshine

The Scribbly Gum is named after the marks on its bark, which are especially noticeable when the bark is freshly cast. These scribbles are the marks of where a species of moth larvae, Scribbly Gum Moth Ogmograptis scribula, have meandered safely beneath the old bark layer, while munching on the fresh growth immediately below. To find out more on the moth and its larva, click here to a link to the Australian museum website.

The zig-zag trail left by a scribbly gum moth larva - its journey began at the thin end of the trail, where the adult moth had laid her egg. The trail ends at the thick end where the larva emerged and crawled into a crevice to form a cocoon. The  adults emerge in the autumn.

Crafty Cockatoo

A mug shot of the robber cockatoo

A few days ago I noticed that someone had seemed to have left the lids off the bins used to store the chicken food - we have chickens roaming free-range in our back yard. Then I saw the lids off again and thought there must be something else to the tale. So, I set up a camera-trap for security surveillance.

It wasn't long before the culprit was caught red-billed. It was a Sulphur-crested Cockatoo Cacatua galerita who was raiding the bins. These are regular, daily, visitors to the garden and they often roost with us up in a high gum tree. They are well-known to be clever birds, so I was not greatly surprised to see who the villain was, but I was surprised at how quickly it adapted to overcome my defences.

Watching from atop the chicken shed

The cocky found it too easy to flip off the lids themselves, even the clip-on lid of the larger bin, so I placed bricks on top of the lids. But, still too easy. The bird simply stepped onto an adjacent bin or tree stump to gain a firm base then used its strong bill to lever open the lids, casting the bricks aside with the lever action. To watch a two minute video of the crafty cocky click here.

The bird opened the large bin first, but as that only contained chicken pellets, it wasn't too happy. It had obviously been watching me feed the chickens and wild birds, noting that I was taking seeds, especially sunflower seeds out of the bins, but which one? It didn't take long to open them all and dive into the bottom of the white bins for the sunflower seeds.

It looked like there was only one bird that had learned how to open the bins as others came and tried, but with no luck. The trick was in stepping back and using the leverage. The clever bird reaped the reward first, facing off contenders before eventually allowing more to join in the feast as it became more satisfied.

There were seven or eight in the flock at one stage, until I heard the commotion and stomped down to the far end of the garden to chase them off.

And the solution - two bricks on each bin, with the bins far enough apart to deny any leverage.

Caught in the act

Koel fledglings

A Koel fledgling is fed by its foster parent - a Red Wattlebird

It's now late summer in Canberra and there are lots of young birds about. So when I heard some loud begging calls from a young bird outside my study window I took a quick look around the back garden, and sure enough I found what I thought I would - a young Common Koel Eudynamys scolopacea. Or rather I found two, one a couple of weeks older than the other.

Common Koels are a species of cuckoo which migrate south to Australia to breed in the southern summer. Then in the autumn, they fly back north to south-east Asia, to the Indonesian archipelago or some other islands in that region. Their full migration and range is not fully understood. With a length of about 450 mm, they are a large cuckoo, the Common Cuckoo Cuculus canorus of Europe is about 330 mm, which is about the length of this bird's foster parent, a Red Wattlebird Anthochaera carunculata (350 mm). So it is a scale up from the European cuckoo.

The older fledgling was a well marked golden bird

The older fledgling had a wonderful golden plumage, with a bold black eyestripe and yellow crown. The younger bird was much less colourful, with a dull grey eyestripe and buff crown.

The younger fledgling - showing how pale its plumage was compared with that of the older bird

Both chicks were being fed by Red Wattlebirds, but I know that another pair of wattlebirds that feed in our garden have raised two broods of their own young this year. Were the Koel chicks both from eggs laid by the same female Koel? If so, the Koel female managed to dupe at least two out of three Wattlebird pairs in our local patch.

Other species used as hosts in south-east Australia that live in the Canberra area are Noisy Friarbirds Philemon corniculatus, although there are none of those around our garden this year; and Magpie Lark Gralina cyanoleuca, but the local pair do not seem to have been parasitised. Virginia Abernethy, who is studying Koels has never found either of these host species used in Canberra either. It seems that the Koels have local specialties in which host species they use.

The younger fledgling begs for food from its busy foster parent

And it received food - of course, what parent could deny such a plea

It was a great opportunity to compare the plumages of the two birds, one older than the other, not by much, but so different in colouring. The older bird was ready to go on with life on its own. It wouldn't be dependent on its foster parents for much longer. Although as I write this a day later, I can still hear both birds calling.

The older fledgling continued to beg too, with a deeper call, and it was fed less frequently

Young Koels often walk through the branches rather than fly

The adult Koels have gone quiet recently now that they stopped breeding for this year. And as they are migratory they will soon be flying north on their annual migration, closely followed by youngsters like these two. I wonder where they will fly to, all alone with no parents to guide them, but with an innate ability to find the species' tropical habitat.

This bird was fully fledged and probably well able to feed for itself - time to go - what a splendid tail

Night watch

An adult female Tawny Frogmouth perched beside her two chicks

Now that the last summer moon is waxing to almost a quarter, it is possible to go out at night and watch the local wildlife without the aid of torchlight. I don't use spotlamps to watch animals as they ruin our night vision, and probably wreck their eyesight too. All we can see is whatever is within the light-zone, outwith that, all is black, darker than if not using a light at all. It is much better to go out at dusk and gradually let your eyes become accustomed to the dark. Anything more than a quarter moon is enough to see under and when there is a full or nearly-full moon I even use binoculars as there is enough light.

The adult delivers a grasshopper to one of the chicks

So, over the past few evenings I have been out watching a family of Tawny Frogmouths with two recently fledged chicks. These youngsters will still be dependent on their parents for about a month after leaving the nest. Frogmouth families typically all roost together during the day, then at dusk the fledglings flit to an open branch, and the adults soon begin bringing food to them. The birds leave their roost about half an hour before full darkness and it is in that first half-hour they are most active. These two adults delivered about ten items per hour for the first hour, mostly within the first half-hour. In the following hour there were no feeds and the two chicks went quiet, snuggled up together and seemed to go to sleep. Not too surprising as the prey items were mostly large grasshoppers which would have probably been more than enough to satisfy the chicks' appetites.

I last saw the adults fly off, presumably to find food for themselves before they would come back and gave the chicks more food. I have used camera traps before to monitor their food delivery times throughout the night and the pattern seems to be; they will bring occasional items during the rest of the night then a few in quick succession as dawn approaches. As with most nocturnal animals, they are more active around dusk and dawn, so those are the best times to watch for them.

At night, Tawny Frogmouths seem to become different birds from the shy ones we see by day. They are so confident under darkness and they do not seem to fear humans. Not only do they allow close approach, but I have had birds fly down to catch insects at my feet (probably stirred up by me) then carry them off to their chicks sitting on a branch a few metres away. Those are the special wildlife moments which we keep in our minds forever.

The two fledglings snuggled up together, head to tail.

Last chicks fledged

A family of Tawny Frogmouths sitting quietly in a tree. As they are nocturnal, they roost by day, relying on their cryptic plumage and minimal movement for concealment from potential predators such as Brown Goshawks. 

The last broods of Tawny Frogmouth Podargus strigoides chicks have finally fledged almost three months after the first broods to do so on 25th October 2014. These final broods fledged on the 16th and 17th January; a brood of one and the other of two, both were from relaid clutches after the adults had lost their first clutches. The pair who finally reared the single chick lost two previous clutches in separate nests to predators unknown (likely Brush-tailed Possum Trichosurus vulpecula). They built a new nest in another tree after each time the eggs were taken, while the pair who reared the twins lost their first brood of chicks after they had left the nest too early. That was possibly after the nesting birds were attacked by a predator, but as these birds are not under constant monitoring, and there was no evidence, we'll never know. They re-used the same nest for their second clutch.

The adult female is on the far left (she has reddish markings on her wings), then the male and two still partially fluffy chicks. Frogmouths usually adopt a 'stick pose' if a potential predator approaches such as a human, but these birds have seen me so often, they know me and here have only partially adopted that pose.

Now that the final results are in I have calculated the breeding success of the sample of Tawny Frogmouth pairs that I study here in Canberra, Australia. I monitored 48 territories this year, similar to most recent years, and most successful pairs (23) reared two chicks, 7 reared three, 8 reared one, another 8 reared none and there were 2 single birds; one male and one female - pity they never met up.

This chick, like so many young fledgling frogmouths, has yet to learn to adopt a protective pose like its parent, in this case mum. Her plumage colouring and posture conceal her well, but I have seen better (see some older posts).

The figure of 17% of pairs not rearing any chicks might seem a high failure rate, but I have recorded almost twice that one year. Overall the breeding success of the population (and that is what matters as all animals must eat to live, including predators) was above average with 1.6 chicks fledged per pair (avg. 1.4), or 1.9 per successful pair (avg. 1.8).

The adults close their eyes and watch one's approach through narrow slitted eyelids. That conceals their bright yellow irides which would betray their camouflage. This chick however, just cannot resist peeping around the branch to watch me with partially open eyes. It will soon learn how to behave safely.

So that ends my study season of Tawny Frogmouths for 2014. It seems a long time since the birds first began building their nests in late July, and it won't be long before July comes around again. For further details of the frogmouths over the season and in previous years click on the links to the right of the page.

What wonderful days and nights I have had with them - great birds.

The male was perched in an adjacent tree, unobtrusive and inconspicuous.

Lesser Wanderer

A Lesser Wanderer basks in the sun while perched on a low twig. 

I was out at The Charcoal Tank Nature Reserve beside West Wyalong, New South Wales, over the weekend (on a bird-banding trip) and there were several of these Lesser Wanderer Danaus chrysippus butterflies flitting about. They all flew low over the ground, landing on the tips of sedges and shrubs in open glades to bask in the sun.

This was a male - the lower wing spots are large and main one has a white centre.
The upper wing spots are also large (previous image).

The species is common and widespread over most of Australia, but not so common in the south-east, so these were just about on the edge of their main range. As they are migratory, perhaps these specimens were pushing south in the height of summer. Or they could have been the offspring of butterflies that had flown south earlier in the year, as the females can lay several sets of eggs per annum.

The head and thorax have a marvelous chequered pattern

As I stalked ever closer and closer to them I gradually realised how boldly the head and  thorax are marked. The black and white pattern is stunning, and out of our usual human scale of perception..

There was a light wind, so the butterflies had to constantly flip their wings wide open,
over-extending them to compensate for the tricky sun-basking conditions

Red Jungle Fowl and descendant breeds

A handsome Red Jungle Fowl in his true colours

Other shots I took while at Taronga zoo in Sydney included these of Red Jungle Fowl Gallus gallus, the wild ancestors of the familiar farmyard chickens. The roosters are spectacular birds with rich golden napes and large red wattles. They are quickly recognisable as related to the farmyard birds.

A hen Red Jungle Fowl with chicks - like domestic hens, she scratches up leaf litter for the chicks to snatch food for themselves, she does not feed them.

The hens are less like their farmyard relatives however, with dull sleek plumage and stiff upright tails. These are perfect adaptations for life in thick forest - their natural habitat in Asia. I reflected on the colours and shape of chicken breeds currently reared in captivity. So, below, I have a dded some examples for comparison and study of how far some have departed from the original wild type. These were all photographed in my own backyard.

A hen Red Jungle fowl crosses a road with her brood - showing off her stiff upright tail. Note how the chicks are all of the same colour, with a broad dark stripe down their backs for camouflage on the forest floor. Domestic chicks usually have a wide variety of colouring, based on this wild type, but very diverse.

A Golden Wyandotte pullet - she has a similar shape as her ancestors,
 with a stiff upright tail and bolder contrasting black and brown feathering

A grey Plymouth Rock hen - similar to the wild type but with grey rather than brown plumage (there are brown varieties of this breed) and a smaller tail

A Light Sussex pullet - she has a heavier build and less flamboyant tail than a wild hen,
and her colour has been selected out to mostly white

A black Pekin bantam - she has an exaggerated tail, much broader than a wild hen,
and her colour has been selectively bred to a dark type.

A white Silkie hen - the colour of the wild type has been lost, her feathers are all fluffy rather than lying tight over her body, and her wings and tail feathers are much reduced

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.