Flocking Time
In the bird world, Autumn is flocking time. Many kinds of birds congregate in flocks in Autumn whereas in Spring and Summer, they are more likely found in pairs or families. It’s now early Winter but there are super-sized flocks still going around.
There is a massive flock of Long-billed Corellas (Cacatua tenuirostris) which roosts at the Yea Wetlands. They turn up towards dusk and the noise is deafening. A friend who had seen a similar flock thought they must nest in vast colonies somewhere, but I was able to point out that flocking is an Autumn-Winter thing. Mating pairs reunite and disperse in Springtime – they are monogamous and mate for life. Then in Summer the parents with their squeaking, demanding young ones hang around in family groups. The whole flock does not breed each year; I think I read that only about 80% breed each year, otherwise there would not be enough nest holes in trees.
This is the time to see murmurations of flocking Starlings (.Sturnus vulgaris). I saw a flock of 25 Straw-necked Ibis (Threskiornis spinikollis), and a feeding flock on a field of Little Ravens (Corvus mellori). Pied Currawongs (Strepera graculina) have built into loose flocks as their numbers in the lowland areas are augmented in the cooler months by altitudinal migration. Even White-winged Choughs (Corcorax melanorhamphos) which are usually in large family groups of 20 or so will form a super flock as I saw one day in Koondrook, consisting of hundreds of birds in a single well-treed paddock.
How does a flock of birds know how to swirl and turn and move together? In Australia, the most legendary flock behaviour is that of Budgerigars (Melopsittacus undulatus) whose large flocks are apparently incredible to watch, turning the sky black, with deafening cries and wonderful acrobatics. I have heard anecdotes that when a flock swoops into perch, there are accidents – broken wings, injuries – but in the main we see incredible coordinated movement when birds are in a flock.
How a flock works is a good life lesson:
1. The whole flock needs to know to head in the same general direction
2. Each bird is responsible to keep reasonably close to the neighbouring birds – don’t get isolated
3. At the same time, each bird is responsible not to crowd their neighbour and become a liability, a cause of interference and crashing.
When these 3 rules are followed, the whole group can respond to the skill and imagination of one another, they can navigate crises together (predators such as falcons), they can benefit from shared knowledge of the landscape, they can get where they are going faster and safer.
I hope you can see, I think all these things apply to human communities and groups. Think about it: shared goals, not too close and not too far, watching out for each other, responding to each other.
Flocking is a good way to live. Join a group and follow these rules.
The toll of the Bell Miner
Everyone used to love the tinkling call of the Bell Miner (Manorina melanophrys), known colloquially as ‘bell birds’. Then word got out about studies that showed they could be a problem in the landscape and they became dreaded more than prized.
Photo: Robert Gardiner
Bell Miners live in fairly large colonies and nest, feed and play in the one area, which they patrol thoroughly, chasing out any pardalote or honeyeater that chances into their territory. And that is the problem: their elimination of the other birds allows certain pests and parasites of eucalypt trees to get a free pass, causing trees within a Bell Miner colonial area to suffer from ‘dieback’ because the predators of the leaf-eaters are kept out. It is called BMAD (Bell Miner Associated Dieback). For instance, lerps are a favourite food of Bell Miners but they never predate the psyllid which produces the lerp, so the psyllids proliferate and cause widespread leaf browning because the pardalotes and Shriketits that might eat them are unable to enter.
When I first came to Yea in 2012, a busy Bell Miner colony around Cummins Lagoon in Yea Wetlands was a guaranteed presence on every visit, yet people told me they had only arrived there after the 2009 fires. It was a perfect site for a Bell Miner colony – they like to be near water and have large trees to patrol. But suddenly, one day, the colony disappeared.
It was about 5 years ago, and they did not move far. They can be heard now, tinkling beautifully down at the Caravan Park where Miller St joins the Melba Highway. It is a distance of only 800m perhaps but since then I have never heard a Bell Miner in Yea Wetlands.
I know of several other stream-side colonies in the district; there is no shortage of these aggressive birds, although they remain confined to their colonial territory. Interestingly, the colonies I have observed in the district have not caused the alleged tree damage for which they have been maligned. The suggestion has been offered that where there is a healthy understorey, it is harder for the miners to keep everyone else out.
So I don’t regret the existence of Bell Miner colonies in our district. Their unforgettable bell-like notes toll clear and beautiful across the landscape. We would be depleted if their story was un-tolled.
The enemy within
Last week after two years and six postponed dates the Spider presentation finally happened. The talk contained many examples of spiders as predators: building webs, ambushing prey. But spiders don’t always get things their own way. They are an integral part of the food chain which means they are often ‘the hunted’. One of the photos shown (pictured left) taken by JB from Limestone shows the insides of a mud wasp nest that had been accidently knocked off a wall. The nest contained several paralysed spiders placed there by the adult wasp. On these spiders eggs had been laid with the intent that when the wasp larvae hatch the spiders would provide fresh food. On one of the spiders you can even see a wasp larva.
I thought that was as gruesome as the night would get until in a discussion after the talk with another JB (from Killingworth) photos and a video were revealed showing a Redback Spider (Latrodectus hasseltii) walking on a carpet (pictured right). When squashed the spider erupted into a ball of writhing worms (pictured below). Alien eat your heart out!
The worms are endoparasitic Mermithid Worms. The worms enter the spider directly or through what the spider eats and they proceed to feed on the internals of the spider without killing it. The spider becomes more and more debilitated until the worms burst out of the body and the spider dies. Because in the final stage of the worms’ lives they are aquatic, before the spider dies the worms induce thirst in the host so that the spider will head towards water. That is probably where the hapless arachnid was going on its trip across the carpet.
I’m not going to upload the video but no sci-fi movie comes close to what happens in nature.
Koalas beware
It seems that this is the season for large moths to appear. The recent rains have caused the Rain Moths to appear in abundance. Another moth that appears in the April/May timeframe is pictured left – a White-stemmed Gum Moth (Chelepteryx collesi). The smaller male moth is pictured. These moths, found in eastern Australia are big with the female wingspan typically being about 16cm across.
But it is the caterpillar that is fascinating. The caterpillar of the White-stemmed Gum Moth (pictured right) is one of the largest in Australia, up to 12cm long. It feeds on the leaves of various eucalypts and paperbarks. The body is covered in very sharp dark red barbed spines (pictured below) that are strong enough to pierce human skin. When touched they break off and embed themselves in the skin causing pain and localized swelling. The spines are difficult to remove.
Before pupating the caterpillar spins a double-walled silk cocoon attached to the side of a tree or in the crevice of bark. It pushes its spines through the cocoon casing to deter predators from disturbing it whilst pupating.
Who’d want to be a koala with these things in your tree.
It’s umbrella time.
This is the time of the year when you will find brown pupa cases lying on the ground (pictured left). They belong to Rain Moths or Waikerie (Abantiades atripalpis). The caterpillars of the Rain Moth live in tunnels underground. They are herbivores feeding on the roots of various acacias and eucalypts particularly the River Red Gum (E. camaldulenis). Their common name is bardi grub, although this name is more correctly attributed to the grubs of the Longicorn Beetle family. The caterpillars pupate underground and move to the surface when the adults are about to emerge. The adults fly off leaving the empty pupa cases sticking out of the ground. This usually happens in Autumn before rain, hence the name. In some areas all the adults emerge on a single night within hours of each other.
Rain Moths are distributed across the southern part of Australia near eucalyptus woodlands. The reference in the title to the umbrella is not due to the rain. The Book of Insect Records from the University of Florida records the Rain Moth as having the highest fecundity (ability to produce offspring) of any non-social insect in the world with a single adult egg count of over 40000 eggs. After mating the eggs are distributed whilst in flight.
Umbrella time indeed!
A Flat Chat
I know people who freak out at the mention of cockroaches. I am disappointed to see that a google search for cockroaches turns up dozens of ‘Pest Control’ sites. Admittedly the cockroaches in our houses – usually the introduced American Cockroach or German Cockroach are garbage collectors and live in the detritus.
When you find a delicate flat fascinating cockroach hiding in the wood pile, however, you have something to wonder at. I haven’t been able to identify this one, but I think it is a type of Bark Cockroach (family Blaberidae) which specialise in being super flat with nothing protruding so they can slip around between a tree and its bark. They are more like a trilobite than those household pesty cockroaches.
The Pattern: look at the beautiful swirly, shiny, intricate design. One writer suggested that the patterns on the back of cockroaches influenced aboriginal art.
The Versatility: in some of the photos, legs and feelers are protruding. When I touched a feeler, it withdrew it out of view. In some photos, no leg or feeler of any kind is visible. When it is rather inelegantly tipped over, the typical six legs and two feelers of an insect are clearly all there; in normal life they keep them well-hidden.
Capacity to Eat Wood: Cockroaches of this type, and wood-dwelling cockroaches in general, can digest rotting wood because their gut harbours the same bacteria that enable termites to digest cellulose.
In the world of cockroaches, this one is flatly fascinating.
Update: The inaturalist website identifies it as Bark Cockroach Laxta granicollis. It is a male because it has wings and the female of this species is wingless.
Opportunist nesters
There is a very productive tree in the Yea Wetlands that hosts nests each season: the big tree growing on the island in Cummins Lagoon at the end near the carpark. Over the last few years, a pair of Australian Ravens refurbish their large pile of sticks and raise another family, while on a slightly lower branch, a pair of White-faced Herons lay eggs and raise chicks. This picture from a previous blog shows the location of the heron’s nest.
Australian birds are opportunists. Their breeding patterns are not totally predictable, depending on the season. It has been a wonderful year for water-birds and wetlands with the high Summer rainfall of a La Nina period. So the White-faced Herons were not content with raising chicks in their usual Spring time-slot, they started a second brood in December. Now they have two chicks from the second breeding currently staring down at the people who pass below.
They often have this strange stiff pose, perhaps a form of cryptic freezing, like a Frogmouth. The position of their eyes on the side of the head means they can see below as well as above.
Bad times will surely come again, so good on the ol’ Herons for breeding up while the going is good.
Carp seize the day
Carpe diem! And that’s what introduced carp (Cyprinus carpio) do! Deliberately introduced into Australian rivers in the 19th century, carp now make up 90% of the fish biomass in the Murray-Darling Basin, including the Yea River and its floodplains.
An old bushman told me once, that when floods come, the carp rush to the furthest tip of the floodwaters, relishing the new ground that the water covers, while native fish – Murray Cod, the perches and catfish – are more hesitant. As the waters begin to recede or dry up, the native fish head back to the main river while the carp keep pushing forward.
Carp make a mess of water – they feed by sucking the mud, filtering out any plant or animal matter it contains with the result that the water where carp live becomes muddy and degraded. They reduce native plant abundance and cause bank erosion, plus the muddy water is less hospitable to many native creatures.
You can see carp stuck in drying pools around the district right now, pools left by a wet Summer but a drier start to Autumn (except for the Northern states, alas!) You can see their fins exposed above the water as they not only seek food, but seek to survive in a shallowing pond.
One year, a Murray River flood filled the large Round Reed lagoon in the Guttrum forest, near Koondrook, and it was a wildlife bonanza with much breeding of waterbirds, frogs, and carp. Then the lagoon began to dry out and millions of carp were stuck while any well-trained local fish had already got out while it was safe to do so. Ducks, herons and egrets preyed on the fingerlings. Then a flotilla of pelicans flew in. They formed circles and rounded up carp into banquets. After a while, they couldn’t get any more because the only ones left were too big even for a pelican’s giant bill – carp can weigh as much as 10kg, though 4-5kg for an adult is more common.
As the water got shallower, the big carp began to flap and excavate ruts and scrapes where the water could be a bit deeper for them, though they still protruded from the top. Sea-eagles, foxes and whistling kites were preying on them. Locals from Koondrook came with trailers to grab a big carp to bury under their passionfruit vines (reported to be super fertiliser), and a pig farmer brought in a truck and pitch-forked out about 10 tonnes for his pigs.
Finally, the water was gone and there were still stinking carp lying all over the lagoon bed. The numbers were incredible! Which is not surprising when a large female can lay 1.5million eggs! Such carnage seemed to have an effect though, for when the lagoon flooded next time a few years later, I did not see many carp at all.
Seizing the day is all very well, but one should plan an escape route for when the day is over.
Biffo at the Blue-banded B&B
Many blogs have been devoted to observations of the life and death struggles occurring at the Blue-banded B&B, an eight metre high wall of a local historic building where Blue-banded Bees (BBB’s) build nests in summer.
BBB’s are solitary bees in that they do not form a collective hive. Instead they tunnel individually into friable materials such as the lime mortar of old buildings and create a cell in which they lay an egg and then stock it with food for when the larva hatches. Whilst the bee is out foraging for this food parasitoid insects such as Cuckoo Bees and Gasteruptiid Wasps enter the cell and lay their own eggs. The BBB’s appeared to be oblivious to these goings-on. This year however I have noticed the BBB’s fighting back.
Cuckoo bees are very obvious about their intent. They will sit on the wall outside a BBB tunnel and wait. When the BBB leaves it enters the tunnel to lay its egg. Sometimes the BBB returns earlier than expected. Pictured above is a BBB (Amegilla sp.) hovering outside its tunnel after having found a Neon Cuckoo Bee (Thyreus nitidulus) about to leave. After about twenty seconds of stand-off the BBB appeared to attack the cuckoo bee (pictured right). All that can really be seen is a melee of antennae and legs but the two fell to the ground and continued the biffo there. They soon separated and flew their different ways.
Blue-banded Bee 1, Invaders 0 – although I think the damage had already been done.
Hiding the Nest
Predators seem to destroy many nests and eat many baby birds. Kookaburras, currawongs, butcherbirds, ravens, even magpies find it hard to resist an easy meal of nestlings. I fear for small urban birds like Grey Fantails and Willie Wagtails as I have witnessed several times the tragedy of hours of work and care – constructing nests, sitting on eggs, feeding young – come to nothing when one of those bigger birds drops by for lunch.
Biologists call it an arms race – the prey bird has to find new ways to outwit or defeat the predator, and there are many intricate strategies, while the predator, in turn, learns new ways to hunt them. Should either prey or predator get too far ahead, the other will struggle to survive.
Some years ago on this blog, Macwake detailed the story of Dusky Woodswallows with a conspicuous nest in a Sheoak losing their brood to some unknown predator: Precarious Position. The story surprised me because I have observed that Woodswallows (genus Artamus) frequently nest cryptically behind a piece of lifted bark on the side of a tree. If they are so foolish as to nest in the open, expect the predators to win the arms race.
I once witnessed a season where a huge mixed flock of White-browed and Masked Woodswallows descended on a Red Gum forest – every spare piece of dislodged bark harboured a nest and the air was alive with busy adults zooming around, feeding the brood.
Here is a Dusky Woodswallow pair (A. cyanopterus) I observed recently with a more typical, cryptic nest site. I never actually could see the babies even though they were obviously being fed and it was only at shoulder-height. The nest is tucked in behind the bark.
My guess is they raised the young successfully.
Focus On Fauna 