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Hanging it out to dry

June 13, 2021

Birds such as Australasian Darters (Anhinga novaehollandiae), pictured left, and Little Pied Cormorants (Microcarbo melanoleucos), pictured below right, can often be seen standing with their wings outstretched drying them in the sun. The assumption many people make is that they lack the ‘preening’ gland at the base of the tail that produces an oil type substance used by waterbirds to waterproof their wings. Darters and cormorants do indeed have the gland. The birds use their heads and beaks to spread the oil through the feathers. There is some debate as to whether the oil actually produces the waterproofing or if the feather structure itself does the job and the oil just keeps the feathers in good condition.

Feathers work by trapping air both to insulate a bird in cold weather and to create buoyancy so that birds such as ducks can sit on the water surface with little effort. Darters and cormorants however dive to catch their food. Having air in their feathers impedes their ability to dive. To reduce their natural buoyancy their wing feathers are wettable so that air bubbles can be shed. This means that they can dive deeper with less effort but the downsize is they need to dry these feathers afterwards.

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So what does it mean when you see a non-diving bird sunning its wings? (pictured left). I don’t know. It’s probably trying to keep its tummy warm.

The perils of being an arborist

June 6, 2021
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I have always thought that arborists particularly those who, wielding chainsaws whilst using ropes to suspend themselves from trees led dangerous lives. Of course if you know what you’re doing it’s probably not as bad as it looks. Unless…

I recently had to call in a group (plantation?) of arborist to fell some dead pines on my property. Everything was going well until a ‘down tools’ was called. An enormous wasp nest was found suspended from one of the branches high up in the tree (pictured left). Buzzing around the nest were what appeared to be, from a distance, some European Wasps (Vespula germanica). Interestingly I could not convince any of the arborists to climb up and get a closer look at the insects for identification purposes!

The nest removal involved me covering myself from head to toe in thick clothing i.e. CFA gear, such that not a bit of skin was exposed and under cover of nightfall and using a red light head torch for lighting knocking the structure down with a large pole. Fortunately the nest was unoccupied.

All social wasps i.e. those which live communally, build nests made of paper. Tree bark and other plant fibres are chewed, mixed with saliva and then molded into shape. At the centre of the nest are the hexagonal chambers where the eggs are laid and the larvae grow. This structure is usually surrounded by a protective paper shell. European wasps, even though they construct nests underground, line the nests with paper using the same technique.

Needless to say that after attacking the nest with a pole none of the brood structure remained intact but the picture above right shows the amazing structure of the external paper shell.

I am not convinced it was the nest of European Wasps. Given it was abandoned, the wasps seen (if in fact they were European ones) may have been scouting around looking for dinner….or a place to doss down for the night.

Different colour, same species #2

May 30, 2021

The last blog attempted to illustrate the (I thought) interesting fact that sometimes birds that look different can be the same species. Apparently the two colour morphs of the Brown Falcon were not different enough to excite anyone about the fact that this was so.

So let’s try again. Crimson Rosellas (Platycercus elegans), pictured left, are widespread through south eastern Australia commonly found in the more forested areas. They feed on a variety of seeds, nectar, berries and nuts as well as invertebrates and their larvae.

En-route whilst driving to Adelaide recently I spotted a Yellow Rosella (pictured right). The scientific name for this parrot is also Platycercus elegans i.e. the same species but clearly a different colour. Scientifically the birds are divided into races – the Crimson Rosella (race: elegans) and the Yellow Rosella (race: flaveolus). To confuse the situation more whilst cycling north through Burra I came across Adelaide Rosellas, pictured below, again Platycercus elegans but the race subadelaidae. Adelaide Rosellas are thought to be the hybrids of Crimson and Yellow Rosellas that are known to mate where their distributions overlap.

Given the definition of a species is that individuals can mate and produce viable, fertile offspring (and clearly this is happening), the three birds are the same species but of different races. The definition of race is very ambiguous.

In the case of the two Brown Falcons from the previous blog, the colour differences are called morphs (not races). The definition of a morph is that the different populations co-exist in the same habitat and can randomly mate with each other. I am not sure how this relates/differs from race.

Clearly I need to consult someone with a greater knowledge of taxonomy. My head hurts!

Different colour, same species #1

May 18, 2021

When considering fauna, particularly birds we are generally pretty good at recognising different genuses. For example we can tell that an Eastern Yellow Robin and a Scarlet Robin are obviously related because of their physical form and their general behaviour. They are of the genus Petroica , rock-dweller, from the Greek words petros for rock and oikos for dwelling place. This reflects the island where the type specimen originates. Furthermore we infer they are different species because of their colour.

But colour is not always a good indicator of species. Brown Falcons (Falco berigora) are found all over Australia and are a common raptor in our district. They come in three colour morphs – pale, intermediate and dark. Pictured above is a pale morph Brown Falcon. Pictured below is also a Brown Falcon but a darker morph. The further you go north the more prevalent is the latter although all colour morphs can exist in all of the range.  The head markings are obviously different as are the colourations on the undersides between the two pictures. But are they different species?

The answer is no. A species is described as a group of animals that can mate and produce viable, fertile offspring. The definition has nothing to do with size colour or shape of the animal. That is why dogs, despite the many and varies shapes and shapes are all one species…they can successfully mate with each other.

As can humans…

Challenge accepted

April 29, 2021

One of the challenges of writing a blog like this is that people bring photos of fauna and expect you to be able to identify them to the species level. Although it is the part of blog writing that turns me on that doesn’t mean it is easy, particularly where insects are concerned. Sometimes the difference between species comes down to genital configuration and I have neither the knowledge nor tools to go there. Moths also present a difficulty simply because of the sheer numbers of species there are in Australia.

Enter Terry Hubbard. Terry sent me with the photo (above) and asked what type of moth it was. Luckily it is the only species of the genus Oenosandra so it’s picture appears in most moth reference websites. It is a Boisduval’s Autumn Moth (Oenosandra boisduvalii) a night flying moth seen in southern Australia and Tasmania in the months of March and April. The larvae feed on various eucalypts.

The female (pictured) and the male look markedly different. The male is a darker grey in colour and is the gender most often seen.

Terry called the photo ‘colliwobbles’ I guess referring to the black stripe on a white wing. What the photo fails to show is that the abdomen is yellow and black striped – a football conundrum that has caused many a family argument.

Mothers Day special

April 24, 2021
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The terms mother and spider do not usually appear together in the same sentence…unless it is something like ‘that Huntsman was the mother of all spiders‘. However Wolf Spiders are one of the few spider species where the mother looks after its young.

A previous blog commented on the discovery of a Wolf Spider carrying around its egg sac, pictured left. Spiders lay their eggs in a woven sac of silk. For many spiders the sac is fixed either within the web or on vegetation, for example under bark. Wolf Spiders do not build webs. They are ambush hunters and can also chase and catch prey. Wolf Spiders and the related Sac Spiders are unique in that they carry their egg sacs with them. A Sac Spiders carries its sac around with its pedipalps, the multi-functional organs at the front of the spider often mistaken for legs. For Wolf Spiders the sac is attached by a line of silk (see photo) to the spinnerets on the abdomen. When walking the spider has to raise its abdomen so that the sac does not drag on the ground.

The Wolf Spider is unique in the spider world in that when the young spiderlings leave the egg sac they climb up the legs of the adult and sit on its back, pictured above. The spiderlings may stay on the mother’s back for several weeks until they are old enough to fend for themselves. Last week Judy B from Limestone, famous for providing photos for this blog of dead things, captured this photograph showing exactly that, a mother spider with spiderlings aboard.

An early Happy Mothers Day to all, including all the Wolf Spider mothers out there.

Why the long face?

April 17, 2021

A horse walks into a bar and the bar-tender says to him ‘Why the long face?’ This is one of the jokes I often use to liven up a party…NOT. But it does remind me of a grasshopper I have just observed whilst on my walk, a Giant Green Slantface (Acrida conica), pictured below.

Also known as the Long-headed Grasshopper, the Slantface is characterised by a conical shaped head and flat sword-shaped antennae. They come both with and without brown longitudinal stripes along the side of the body.

They are slow moving insects but have a number of defences that prevent them from easily being attacked by predators. The first is camouflage. In the grass on which it feeds it is very hard to detect, even if you know where it has flown. When in flight the grasshopper displays a red abdomen that serves as a warning to predators not to attack.

Like crickets, cockroaches and other related insects the Slantface lifecycle is one of incomplete metamorphosis i.e. the young instars look exactly like the adult (except they don’t have wings) and go through a series of moulting stages as they grow to big for their shells. Eventually the adult emerges and flies off.

Sort of like getting your P-plates in humans.

Follow the leader

April 9, 2021

Processionary caterpillars (Ochrogaster lunifer) are the larvae of Bag-shelter Moths. At this time of the year they can be found feeding mainly on acacias and grevilleas. As the name suggests the caterpillars shelter in a bag made of silk usually situated in or the base of a food tree.

When a given tree has been defoliated the caterpillars move to find another food source. The lead caterpillar leaves a physical trail in the form of a silken thread as well as a pheromone trail which successive caterpillars will follow head to tail in lines up to several hundred individuals. The picture below shows a procession of only a handful of individuals – I guess trying to walk up the bike path is asking for the silken thread to be periodically wiped out by passing cyclists. A processionary line is also formed when the caterpillars look for a suitable location to pupate (underground).

Both the caterpillars and the adults are covered in fine hairs. These are quite poisonous as they contain an anti-coagulant that can cause hives if touched. The fine hairs from the caterpillars are also suspected to cause premature abortion of the foals in horses.

Not everything fluffy is cute and cuddly!

A gulp of swallows

April 4, 2021

The title of this blog was going to be the punch-line until I looked up the collective noun for swallows and found out that it actually was gulp, as well as flight, herd, kettle, richness and swoop.

Swallows are widespread throughout Australia. Two species of swallows and two species of martins, also of the swallow family, occur in this district. Martins are distinguished from swallows by the square-shaped tail. Both swallows and martins are highly gregarious and are often seen in mixed flocks perched along fence lines (pictured below) in this case Welcome Swallows (Hirundo neoxena) and Tree Martins (Petrochelidon nigricans).

Welcome Swallows (blue head, brown face) and Tree Martins (grey)

Welcome Swallows (pictured left) are probably the best known of the group as they have adapted well to human habitation, frequently building its nest under the eaves of man-made structures. Tree Martins on the other hand nest in natural hollows that they line with grass and leaves. Both are acrobatic aerial feeders of insects, the martins at tree top level and the swallows lower down.

Also around at the moment are Dusky Woodswallows (Artamus cyanopterus), pictured right. They are also active insectivores. Named for their swallow-like tail Dusky Woodswallows are not actually members of the swallow family but are grouped with butcherbirds, currawongs and magpies.

Gulp!

As plain as black and white

March 30, 2021

A lot has been said about the LBJ’s (little brown jobs) – those hard to identify birds that flit around the treetops. At the moment I am having trouble identifying B&W’s (black and white) birds.

Willy Wagtail

It must have been a bumper breeding season for Willy Wagtails (Rhipidura leucophrys) this year. They seem to be everywhere. Wagtails are a type of fantail so called because of the habit of wagging their tails when foraging on the ground for insects. They aggressively protect their territory particularly nesting sites and will chase off much larger ‘chick-stealing’ birds such as magpies, currawongs and kookaburras. Wagtails inhabit most habitats except dense forests. At Flowerdale on our open-forested land I have never seen them on the property but will often see them on the boundary fence next to the neighbour’s open pasture.

Restless Flycatcher

The other black and white bird around at the moment that superficially looks the same as a Willie Wagtail but is more slender is the Restless Flycatcher (Myiagra inquieta). It is one of several flycatcher species in the district. The Restless Flycatcher is distinguished from other flycatchers by its white throat. Like the Willie Wagtail it is also an insectivore, the Flycatcher preferring to hunt mid-canopy, rarely on the ground.

Pictured side by side the differences are obvious. The Flycatcher lacks the black throat and white eyebrow of the Wagtail. They are more easily distinguished at a distance by their calls. The Willie Wagtail has the familiar ‘chittering’ sound whereas the Restless Flycatcher has an unusual ‘scissor-grinding’ sound.

Restless Flycatcher call (below)

Restless Flycatcher
Willy Wagtail

Discernment is sometimes in the ‘ear of the beholder’.