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Round robin

April 20, 2019


 
On hearing a kerfuffle at the back door, we looked out to see a plump yellow and grey bird fluttering and then landing on a beam under the eaves. It was an Eastern Yellow Robin which seemed distressed and confused, perhaps having been chased by another bird: currawong, butcherbird or even our often-seen brown goshawk – who knows? After about 15 minutes, it had settled down enough to fly off, but in the meantime, we had a chance to have a close look at this lovely little bird.


The Eastern Yellow Robin is mostly sedentary and can be seen or heard occasionally, all year round, in native vegetation remnants, roadsides, creeklines and even gardens in the King Parrot catchment.

Both sexes emit a persistent piping call, sometimes in lengthy bursts. The male also gives a loud two- or three-note territorial call. Both calls can be heard by clicking on the audio bar below.
 
 
Birds like this robin must be doing it tough in this extended extremely dry period, with food sources depleted. So here’s hoping for a break in the weather soon!

A climbing wombat?

April 7, 2019

We couldn’t resist posting this fine picture of a Koala (Phascolarctos cinereus) that was sent to us by Ian from the Yellow Creek Dairy Creek Landcare Group. The koala sauntered past Ian as he was fencing on his property near Yea.

Koalas are a relatively rare occurrence in our district. There have been only 9 recorded since 2000 on the Victorian Biodiversity Atlas data base within a 15 km radius of Ian’s property – an area that includes Flowerdale and Strath Creek. A few of the sightings have been animals translocated from French Island to Mt. Disappointment Forest in 2004.

It is interesting to ponder the ancestry of koalas. They are quite agile (though vulnerable) on the ground and are not at first sight obviously adapted for arboreal existence: dumpy, no prehensile tail (or any tail to speak of!), no gliding membranes and relatively small forward-facing eyes not particularly suited to night-time manoeuvring among branches. To compensate for these deficiencies they do of course have powerful hands and feet with long sharp claws.

So what are the roots of this unique creature? Apparently the fossil records provide very little information about the origins of koalas and their relationship to other marsupials. Comparisons with the characteristics of living marsupials offer the best clues, and it turns out that koalas share many features with wombats, such as a rudimentary tail, a backward-opening pouch with only two teats, granulated rather than ridged pads on the hands and feet, cheek pouches, a unique gastric gland – and they even have similar hook-shaped sperm quite different from those of other marsupials.

All these mutual characteristics led biologists to deduce that the koala shared a common ancestor with the wombat. Furthermore, that ancestor was almost certainly terrestrial (ground-dwelling) – more wombat than koala!

On a scale of 1 to 10

April 4, 2019

Those who read this blog regularly will know that the Order of insects known as Hemiptera, insects with sucking mouthparts, feature regularly. We have featured cicadas, shield bugs, gumtree hoppers and psyllids.

Another common but rarely noticed Hemipteran is the scale insect. Scale insects are parasites of plants sucking their sap. The female is wingless and usually immobile, attaching itself onto a plant and then secreting a wax covering to protect itself. A common scale insect locally is the Gum-tree Scale (Eriococcus coriaceus), recognised by their housings, groups of white sacs on eucalyptus twigs and branches (see below).

gumtree scale 1-DSCN2302

The sac is the house of an adult female scale insect. The insect itself has its mouthparts attached to the plant and the opening at the top of the sac is blocked by its abdomen. A by-product of feeding, as with many Hemipterans, is a sugar-rich substance called honeydew. This is extruded from the hole in the top of the sac (see picture above). Scale insects have developed a symbiotic relationship with ants which collect the honeydew as a food source in return for protection from predators and parasites.

After each moulting both male and female scale insect instars find new positions on the plant and construct new wax sacs. After the final moulting the adult female insect constructs the final sac which takes up to two weeks. During this time the female is fertilised. Several hundred eggs are laid in the sac and when hatched the resultant nymphs emerge from the hole in the sac and crawl or are blown to other plant locations or plants to which they attached themselves.

Adult male scale insects do not have mouthparts with which to feed nor do they construct wax sacs. Their sole purpose is to mate with females, after which they die. This occurs over a few days.

Natural predators include birds such as Blackbirds and Silvereyes, the caterpillars of some moths and the adult and larval forms of Ladybird Beetles.

On balance, scale insects are quite interesting.

The skill of the twitch

March 27, 2019

At first sight the art of twitching (bird watching) seems fairly easy – memorise from a reputable bird book all the birds in your area and then observe them in the wild. It is only when you hang around with a group of twitchers do you realise the complexities that lie within this past-time. Veterans to the game can not only identify the birds by sight, they can do it by bird call. There is an added layer of difficulty when immature birds get thrown into the mix. It then becomes apparent just how much knowledge some twitchers have.

Olive-backed Orioles (Oriolus sagittatus) have been calling in the district and there are young ones about (see picture above left). Apart from their distinctive call the pattern on the breast is a give-away.  Paint the beak orange and make the eye red and voila, you have an adult Oriole (pictured right). Easy right?

Similarly, the difference in appearance between an immature (left) and adult (below) Grey Shrike-Thrush (Colluricincla harmonica) is also about colouration, in this case the immature bird has a tan eyebrow and tan wing edges. Of course if you are in the know you will know that the adult pictured is a male – the lores (the area between the eye and the beak) is white not grey. OK, a bit trickier but still relatively simple.

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I am always impressed though by twitchers who can identify the differences between the many Australian raptors – kites, kestrels, falcons, goshawks, hobbies, etc.  I asked a twitcher friend to identify the bird in a photo I had taken (left). He immediately said a Spotted Harrier (Circus assimilis) and then after about half a minute of looking at the photo said ‘Second year bird’.

What a geek! (Apologies to P.M., outstanding knowledge!)

A hive of activity, still

March 21, 2019
by

Despite the fact that many Australian native bees do not form a hive, and that the Blue-banded Bees have left the vicinity, the Blue-banded B&B recently described is still a hive of activity. The Blue-banded Bees have gone and so too have their parasitic predators, the Cuckoo Bees and the Gasteruptiid Wasps.

The B&B is still buzzing though. At the base of the lime-mortared brickwork is a bluestone block, originally the base of the loading bay entrance. Drilled into the block for reasons time has forgotten are a series of holes. In recent days orange and black wasps have been building nests of mud in those holes. Also investigating the holes have been Cuckoo Wasps (I think), pictured left. They are not wingless although the photograph makes them look so.  The Cuckoo Wasps have been busy checking all the holes … except one!

Cuckoo Wasps are typically iridescent green or blue. As the name suggests they are a parasitic wasp laying their eggs in the nest of their host, in this case Mud-Dauber Wasps. When the Cuckoo Wasp eggs hatch the larvae eat the food that has been stored for the Mud-dauber young and then when the Mud-daubers larvae hatch they eat them as well.

Back to the hole which was avoided by the Cuckoo Wasp … sitting inside was one of the orange and black wasps, no doubt protecting the nest. But for how long? At some point in time one imagines it will have to go out and feed and the Cuckoo Wasp will pounce.

Unfortunately there’s no room service at the Blue-banded B&B.

Preying on the mantis

March 13, 2019

An ovipositor is a structure used by some animals to lays eggs. For insects it is situated at the end of the abdomen, see picture left.  The organ can be highly modified. In sawflies the ovipositor has been modified as a saw-like tool to slice open leaves into which eggs are laid. In grasshoppers and crickets the ovipositor acts as a shovel to dig holes in the ground. The eggs are then laid in the resulting chamber. The ovipositor in many hymenopterans (ants, bees and wasps) has been modified for stinging or piercing, many having associated venom glands. Parasitic wasps in particular use the ovipositor to drill into a substrate so as to be able to deposit eggs directly on the host body.

Marie on Junction Hill has been carefully watching a praying mantis egg-case (known as an ootheca, see picture right) that has been deposited on a plant outside the kitchen window, waiting for the moment in which the young mantises emerge. Recently however a Mantis Parasitic Wasp (Podagrion sp.) has been loitering about the ootheca, see photo below. The word Podagrion is derived from the Greek podagra meaning gout, referring to the wasp’s swollen hind legs (see pictured above).


Using the ovipositor as a drill the female wasp pushes it into the egg-case and deposits its eggs onto the eggs of the praying mantis. When the wasp eggs hatch they eat the mantis eggs. The holes in the side of the ootheca indicate some young wasps have already emerged.

Depending on the species an ootheca can contain up to several hundred eggs. Hopefully Marie still has a chance of photographing some of the baby mantises hatching.

 

Reflections on dung

March 8, 2019

When we think of dung beetles (which admittedly is not that often), we tend to think of the two dozen or so species that were introduced by the CSIRO to aid the dispersal of cattle dung and thus reduce the problems of pasture fouling and fly breeding. But Australia has its own dung beetle fauna – apparently more than 500 species! Although some of these will tackle cattle dung, the denser, drier fibrous pellets of native marsupials are much more to their liking.

Walking past a patch of decomposing Common Wombat scats we noticed movement and, on inspection, active below the surface were several dung beetles. One of the beetles is shown in the photo above, and was identified by our dung beetle guru, Bertram Lobert, as most probably Onthophagus australis, a native species that can also be abundant in cattle dung at times. So we started to take a greater interest in the faeces of our local wombats, and discovered that the relatively rapid breakdown by dung beetles appears to be a rarity – most of the cube-shaped pellets seem to hang around for some time, hardening and fading before eventually crumbling.

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As well as wombats, there are plenty of Eastern Grey Kangaroos on our property at present and, as far as we can tell, there are no dung beetles active in their numerous droppings – like the wombat scats, the pellets just dry over time and eventually crumble to dust, so that there is a range of shades from almost shiny black fresh scats to very pale older ones.

This got us thinking: have native dung beetle numbers declined? And if so, is it due to human agricultural activity – such as use of chemicals, soil compaction, mechanical disturbance, etc. Or have the beetles simply gone with the flow, so to speak, and switched to the more abundant and readily available cattle dung?

We have no answers and would welcome any comment. Results of internet searches are dominated by articles and information on introduced dung beetle species. However we did come across an article by Nicole Coggan titled Are Native Dung Beetle Species Following Mammals in the Critical Weight Range towards Extinction? which considers dung beetles in relation to small native mammals, but not kangaroos or wombats.

It would be a great pity if native dung beetles are declining, because one of the services they provide is to tunnel, sometimes quite deeply, into the soil to bury dung, thus not only enriching the soil, but also improving rain penetration. We’ll continue to keep a scatological eye on what we have available.