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.
How I spent my summer
To make sure that I get the most out of my summer holidays I usually set myself some goals, for example, read a novel a week. One of my goals this summer was to get a photograph clearly showing why the Spotted-eye Hoverfly (Eristalinus sp.) was thus called. It seemed like an easy task but these insects are very active fliers and very aware of anything new in their environment, like a photographer.
Hover flies are one of the major groups of pollinating insects, visiting a wide range of flowers, with the adults feeding exclusively on nectar and pollen. Some hoverflies only pollinate one flower species. Hoverflies of the genus Eristalinus are characterized by distinctive eye markings. Their larvae live in aquatic and semi-aquatic environments and have the ability to filter and purify water.
After five weeks of racing around a variety of white or pale-yellow flowered bushes I have ONE semi-decent photo (below).
Job done. Now on to the next goal. Where am I going to find a female Feather-horned Beetle???
2022 Minimalist nest design award
Finalist 1 – Tawny Towers (left)
Architect: Tawny Frogmouth (Podargus strigoides)
Location: Horizontal branch, Flowerdale
Materials: Twigs, loosely dropped into place, grass and leaf lining
Affordability: 3 stars – minimal use of materials, all recycled
Stability: 1 star – very flimsy, easily blown down in a storm
Finalist 2 – Plover Pad (below)
Architect: Masked Lapwing (Vanellus miles)
Location: Middle of the Flowerdale Recreation Reserve
Materials: A few sticks of grass laid out on the ground
Affordability: 4 stars – very minimal use of materials, all recycled
Stability: 3 stars – can’t fall down, minimally camouflaged, could be stepped on
Finalist 3 – Dotterel’s Dive (above)
Architect: Black-fronted Dotterel (Elseyornis melanops)
Location: Middle of the amphitheatre, Euroa Arboretum
Materials: nothing, a depression in the rocks
Affordability: 5 stars – you get what you pay for!
Stability: 5 stars – built of stone, can’t fall down, highly camouflaged
And the winner is … the Black-fronted Dotterel. Congratulations. An honorable mention goes to the Bush-stone Curlew and the Plains Wanderer.
Go turtles!
The gum leaves in summer seem to be decorated with their own Xmas ornaments – a variety of lumps and bumps. These adornments are usually due to insects that lay their eggs either in or on the leaves, insects such as gall wasps, sawflies and eucalyptus bugs. One decoration that caught my eye this year appeared to be a type of ruff encircling a eucalypt stem (pictured left). The structure, presumably an egg case was hard to identify on the internet. As pointed out in an earlier blog it is hard enough to identify an adult insect from a photo, let alone its young or worse still its eggs – if indeed it was an insect that caused it.
In such a case the tried and true method of simply waiting and watching the object was called for although a more thorough search of the same tree revealed other egg clusters, some more advanced in the lifecycle. Luckily the waiting phase was minimized.
The photograph above shows that out of one such cluster small grubs emerged and then made their way along the stem to the nearest leaf where they joined their ‘hatching cohort’ devouring gum leaves. These are the larvae of Eucalyptus Leaf Beetles, beetles that sort of look like Ladybird Beetles but are bigger (click HERE for related blog).
The life of the grub however is not easy. There are all sorts of perils along the way. Pictured right is a predatory Shield Bug nymph attacking a beetle grub. It stabs the grub with its rostrum through which it pumps in digestive juices and then sucks out the nutrients.
It was like watching one of those nature documentaries where young turtles hatch and try and make their way down the beach to the safety of the ocean before the seagulls eat them. I always root for the turtles. This grub didn’t make it.
It’s a … thornbill!
Thornbills are one of the most difficult bird groups to distinguish. I knew one birder who gave up birdwatching because she “got sick of staring at thornbills trying to guess what kind they were” and took up botany instead – plants don’t fly away.
We have five species of Acanthiza – the thornbill family – in the district: Brown, Striated, Yellow, Yellow-rumped and Buff-rumped. Plus there is the weebill (Smicrornis brevirostris) which is like a thornbill except that it has a ‘wee’ bill instead of a ‘thorn’, that is, its beak is shorter and fatter – it is also Australia’s smallest bird.
All thornbills build dome nests with a side entrance and are insect-eaters primarily.
Learning thornbills is indeed too complicated and exacting to interest many people, so I will suggest one simple distinction: two of them forage on the ground; the rest never leave the trees.
The Yellow-rumped and Buff-rumped are ground foragers. Although they use trees for nesting and sleeping and refuge, they feed in busy little flocks on the ground.
All you have to decide then is whether the yellow colour on the rump (only visible when they open their wings usually) is bright yellow or dull yellow (=buff), which sounds easy, right?
Also the Yellow-rumped has brown eyes and the Buff-rumped has white eyes, which is another distinction hard to make from a distance.
Perhaps it would be sufficient to say “Thornbill!” and be glad that these delightful little creatures share our glorious planet.
Leave the identification to pedants.
Skewered!
This blog site has featured many articles about Hemipterans, an order of insects that includes cicadas, psyllids and various other types of ‘bugs’. Amongst other things these insects are characterised by having sucking mouthparts known as rostrums. The rostrum is capable of piercing and consists of two tubes. One facilitates the injection of saliva into a food source. The saliva contains enzymes that dissolve cellular material. The second tube allows the insect to suck out the pre-digested liquid.
Whereas psyllids, gum-leaf hoppers, spittlebugs and the like suck sap from plants there is a group of Hemipterans that are predatory and feed on other invertebrates. The Orange Assassin Bug (Gminatus australis) is one such creature. When ‘at rest’ the rostrum is tucked underneath the body (see picture above).
The Assassin Bug is an ambush predator that grabs passing prey with its front legs before stabbing it with its rostrum, injecting enzymes and sucking out the liquid food. The legs are haired to help grip the prey. The unlucky victim pictured above is a Horned Treehopper (Ceraon sp.).
Interestingly both predator and prey are Hemipterans. I guess ‘Who lives by the rostrum, dies by the rostrum’.
Hidden in plain sight
The fly family Syrphidae comprises insects commonly known as Hover Flies. Adult hover flies feed on nectar and pollen and are often found ‘hovering’ around flowers, hence the name. They are an important pollinating group of insects.
Hover flies are harmless to humans having no biting or stinging capability. This harmlessness makes them susceptible to predation. To mitigate this hover flies exhibit Batesian mimicry to different extents. Batesian mimicry is a form of biological resemblance whereby a harmless organism e.g. a hover fly, mimics an organism with warning capability i.e. sting or colouration, with the hope that it is mistaken for something dangerous and left alone. At the minimum this mimicry in hoverflies consists of black and yellow colouring so as to resemble bees. The previous insect blog described the mimicking characteristics of a harmless drone fly, a species of hover fly.
At the moment Sweet Bursaria (Bursaria spinosa) is flowering attracting many species of insects (and insect photographers!). Yesterday’s ‘find’ was a black and yellow wasp, pictured above. Trying to identify it proved more difficult than photographing it. After several hours of unsuccessful research I noticed the antennae of the insect were short and stubby, pictured below, much more fly-like than long, bent wasp antennae. Another hour of trawling the web revealed the creature to be a Wasp-mimic Hover Fly (Ceriana (Sphiximorpha) breviscapa). Unless you are close enough to note it only has one pair of wings and those antennae, it looks for all intents and purposes like a more dangerous Potter Wasp.
Batesian mimicry to the max!
Focus On Fauna 