Double Dagger Art Stories

Fire and managing the damage

back burn

Nurturing Fire

Bushfire may be the most extreme ecological change we can witness, it is destructive,  it is inevitable, and it is necessary. Fire is essential to the ecology of most plant communities in the Royal National Park. Our flora is largely adapted to fire with strategies to regrow and reproduce after a fire event. Many plants depend on this fire response to complete the life cycle. Some marsupial reproduction may also be geared to take advantage of the green pick that flourishes after fire. In past millennia under aboriginal care there have been seasonal fires lit with the purpose of increasing accessibility and the productivity of the country. There is good reason to assume that our notion of an ideal natural environment should include more fire, but there are limits:

Damaging Fires

  1. Too hot. Fire that escapes into the canopy of the trees will kill a range of plants and the animals that take refuge in treetops. When the landscape is renewed there will be a suite of plant and animal species missing, diversity will suffer.
  2. Too extensive. Fire that is uncontrolled will burn longer and further, the sheer scale of destruction will produce additional destructive effects.  Where fires are controlled and restricted to a small scale there is a mosaic pattern of burnt and unburnt land, this allows for movement of animals between different areas and recolonisation after fire. Likewise, plant species that are burnt in smaller patches will be more likely to re-establish after fire. In a parcel of bushland surrounded by a cleared landscape there can be little re-colonisation from the surrounding area.
  3. Too frequent. The re-establishment of life after the fire takes time. Plants that regrow from seed take time to mature and set new seed, animals also take time to recolonise after the plant life rebounds. The fire alters the physical landscape too, soil and rocks are baked, beds of ash cover the hills and move into the creek beds, all this takes time to return to stasis.Curramoors fireCurra Moors 6hrs

Fire management

Controlled ecological burns do take place in the Royal under the National Park and Wildlife Services. These fires are infrequent and subject to limited staff numbers and equipment, by comparison the Rural Fire Service is well resourced. The RFS is given the responsibility to conduct hazard reduction burns to protect housing adjoining bushland. When fire in the park is out of control command is given over to the RFS and while the NPWS will continue to assist, the task of managing risk and taking  strategic decisions rest with the RFS. The priority of the RFS is to protect human life, of the public and of the firefighters, then to protect property. Risking life to protect the bush is perhaps a low priority. Putting out the fire is the objective and this should be done safely and as easily as possible. Ecological objectives are not forgotten but they are weighed up somewhere in the mix. There are a raft of issues that create a tension between good ecological management and effective fire control, remembering that poor fire control can lead to disastrous ecological outcomes:

  1. Back burning. One way to stop a fire is to remove fuel in its path. If there is sufficient time, and the wind feeding the fire is favourable, and if there is good access, it is then easy to set a line of controlled fire that will advance towards the oncoming wildfire. When the two fires meet they will subside having burnt everything on the fire ground. The back burn will usually  be set where there is vehicular access to allow for water tankers to protect the fire fighters and guard against the possibility that the back burn will itself go out of control. This strategy means that a large area of land may be burnt  between the back burn and the wildfire and fleeing wildlife will be trapped between the two fires. The back burn may be set on land that would not necessarily burn if left alone. Perhaps a gully with moist vegetation that would not necessarily set fire by normal ember attack, and this artificial fire will be burn with greater speed, uphill rather than down, again trapping escaping wildlife. Again the cost of doing nothing must be weighed against the cost of taking practical action. There may be alternative strategies, like proceeding into the bush away from the protection of the tankers, but this carries greater risk, again an exercise in balancing costs. backburn 2Lady Carrington drive
  2. Water. Another way to put out a fire is to douse it with water, if that water comes from the ocean it will contain salt that will stay in the soil and prevent plants from growing. The bare landscape will then be open to erosion and soil will be lost and watercourses will be choked with increased sediment. The tankers refill from fresh water sources, weirs and hydrants, but the choppers are able to scoop water from the beaches, and where the ocean is close it may save valuable flying time. saltwater scaring1An Erickson skycrane was filmed taking seawater from Garrie beach for the Curra Moors fire and there was some minority social media comment made about the damage to the environment. The public appetite seemed to be extinguish at any cost, but it was reassuring  that RFS Sutherland fire control were quick to post other clips and shots of choppers taking water from freshwater sources. Using saltwater is a known problem and should be an option of last resort. It may be that the RFS fire control is more open to ecological concerns than the general public. When it comes to the fear of fire the bush becomes an enemy and those who are concerned for the bush become caught in an ideological war where lives and houses are seen to trump all other concerns, no matter how distant the fire threat may be. chopper waterhole
  3. Fire retardant. The most expensive way to deal with fire is to use a chemical retardant. In this fire retardant was spread by use of a Very Large Air Tanker, a modified DC8, with a reputed cost of $40000 per drop of bright pink retardant. While not as damaging as salt water the retardant does contain high levels of ammonia which will alter the growing conditions for plants, especially in or near the waterways. Here are some extracts from an RFS factsheet on fire retardants:

    The NSW RFS drops fire suppressant retardants and gels such as Phos-Check®, Blazetamer and Thermo-Gel from aircraft during firefighting operations to help slow the spread of a fire.

    Long-term fire suppressants such as retardants are essentially fertilisers (ammonium and diammonium sulphate and ammonium phosphate), with thickeners (guar gum) and corrosion inhibitors (for aircraft safety).

    Sometimes a red coloured pigment, made from iron oxide, is added so that those spraying can see where they have released the fire retardant. Examples are Phos-Chek MVP-fx and Phos-Chek 259-F.

    Short-term fire suppressant foams are made of a combination of wetting agents and foaming chemicals, mixed with water. This allows the water to penetrate surfaces more easily. Their usefulness is limited against high-intensity fires, where long-term retardants have proven more successful. Examples are Angus ForExpan S, and Phos-Chek WD-881.

    retardentVLAT

  4. Containment. When the fire is surrounded by burnt out land the fire will subside and eventually die out. After the flames die there will be trees and logs that continue to smoulder and gusty winds can restart new fires.  This protracted period of danger can be shortened if all land within the containment lines is burnt out quickly. The burning can be accelerated by the use of aerial incendiaries. This need to bring the fire to a quick end may run counter to good ecological management, it may be better if the fire ground retained patchy areas of burnt and unburnt vegetation.

Clean Up. After the fire there is further work to be done that may have environmental consequences. Burnt trees are sometimes unstable and may represent a risk to the public if they were to fall on the roadway; black tree, black road – an accident waiting to happen. These burnt trees also have habitat value for wildlife, many birds, bats and possums nest or roost inside the shelter created by the sculpting effect of fire. Many species are entirely dependent on these hollows to reproduce. It would be good if tree felling after the fire was sensitive to these ecological values.

Contaminants will arise from the destruction of infrastructure. There was a time when all the “hardware” in the park was made of timber or steel, but now the use of plastics has gained a foothold. Roadside markers are now made of plastic and these wilt in the radiant heat, but more worrying are the kilometres of fibreglass footpaths that turn into fine filaments that will remain as permanent detritus in the park. The walk to Wedding Cake rock was unaffected by this fire but the section of new track north of Garrie beach has been burnt out. Clean up will involve careful raking and removal of all affected topsoil.

walkway

 

Posts

Deer

deer elvis

Meet Elvis the deer in his prime, antlers aloft, coat shiny and sleek. This photo was taken back in the winter breeding season when good looks are important. In the heat of summer the antlers have been shed and the fur is looking mangy. Deer herds are now congregating under the shade of safe houses where they have easy access to water and a daily feed of vegetable scraps and treats. Older males and younger bucks seem to get along at this time of year. When the sun goes down the deer are up and about trimming the grassy lawns down to a perfect stubble. The urban deer will take refuge in the bush if they are threatened, but it seems they have reached an arrangement in Maianbar of live and let live. Of course they are an ecological nightmare, but that’s another story.

jingle bells

Posts

Red Flag

Trigger warning, a few pictures of a dead animal follow, also some material of a sexual nature, but be assured no cruelty or misadventure is indicated.

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Out on my daily walk I came across a little dead mammal on a bush track. Strange. Dead animals are not usually left animals alone for long making a handy meal for the many scavengers of the bush; rats, monitors, owls, foxes. I bent down and had a sniff, it smelt a little, maybe it and been dead for a day or two. The eyes were receding. I noticed it had a pointy snout and little serrated teeth like a steak knife. It was an Antichinus, a small carnivorous marsupial “mouse”. I took a couple of photos in the fading light and wandered on thinking about how and why the animal came to be lying there. Dead as a doornail.

For the sake of comparison here below are two skulls, a Brown Antechinus (a) on the left and a mouse on the right (b). Notice the large protruding incisors of the rodent compared to the long row of teeth in the antechinus. Note also the pointed arrangement of toes on the feet of the antechinus and the toes of the antechinus are separated while they are fused in the mouse.

Skulls

Some way down the track I stopped and turned back to check for testicles. Sure enough, bold as brass, a huge scrotal sac, indicating a dead male antechinus. The cause of death now obvious, over-exertion during breeding season. Facts furnished here by the Australian Museum “Males live for approximately 11 months and have a short breeding cycle of about 2 weeks in winter, after which they die as a result of stress and exhaustion. Females give birth to undeveloped naked young that latch onto teats in the pouch for up to 50 days. The pouch is an open slit found on the belly.”

Brown antechinus fact sheet

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Going out on a limb

In identifying a plant one is often making a guess. An educated guess is still a guess and sometimes there is no correct answer. Many of the banksias belong to groups known as complexes. Members of the complex are seen as separate species but they can also hybridise – meaning that they may have intermediate forms. Any one plant may have a variety of different features, sometimes typical, sometimes weirdly different. Sometimes the scientific name serves to obscure the identity of a plant, take Banksia oblogifolia, it is supposed to have oblong shaped leaves, where the tip is blunt and the base of the leaf is relatively broad. As it happens the leaf shape is variable, and the most reliable identifying feature is a rusty coloured felt that covers the midrib and young branches. The scientific name may endure even if it is misleading because the history of the name is seen as important. The type specimens of banksia oblongifolia may have had particularly oblong leaves, but specimens from further afield may not fit in the box.

banksia oblongifolia

Bus Stop banksias

Behind the artfully decorated Maianbar bus stop there are half a dozen species of banksia within a short walk. To identify them it is handy to learn their names. The information within the name will jog the memory each time you try to identify a plant. Plants may have a common name and a scientific name, both names can be useful. The common name is least reliable, it will vary from place to place and can be pretty vague. The scientific name will slot the plant into the taxonomic hierarchy which will tell you much about the structure of the plant and how it relates to others. The scientific name can change when academics get busy, but it will lead back to the first scientific description of the plant. The scientific name is a double-barrelled binomial usually composed of latin or greek roots or a nod to a dignitary, explorer or a botanist. All of this is useful information.

In the photo below is Banksia spinulosa, the hairpin banksia. The old fashioned hairpin is now an uncommon object and so the common name is possibly not very useful. The generic name Banksia was conjured up in 1782 by Carl Linnaeus the younger, son of daddy Carl Linnaeus the swedish naturalist who invented the taxonomic system. The first half of the binomial honours Joseph Banks who collected the original type specimen in 1770 on Cooks “voyage of discovery”. The second part of the name refers to spines on the leaf tip.

 

Banksia spinulosa
Am liking the common name now that I see what an old fashioned hairpin from 1850 looks like. It has points on the end that would give you a little jab like little spines, whereas the modern bobby pin is not nearly so fearsome. But all jabbing aside the rounded end of either style of pin resembles the bent anthers of the rows of flowers.

 

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Bashing the big Banksias

Bansia ericafolia

May 15 2017
Tis the time of year when Banksia ericafolia is in full bloom. This shrub is common up on the heathland (the name erica refers to South African heath, which has a similar leaf shape). Other Banksias flower at different times providing honeyeaters with a reliable supply of food, but B, ericifolia is the most bountiful. Early settlers were shown how it was a source of bush tucker for aboriginal people. You can run your hand over the cone and lick off nectar or soak them in water for a sweet drink. So abundant is the nectar that you can see droplets glistening on the flowers and dripping from the branches, on the ground below there may be ants feeding. In the photo notice the damp patch at the base of the flower cone and droplets among the flowers.

 

Scientific literature (yawn…)

Unlike social media the scientific literature does not repay the urge for instant gratification, the gems are buried deep.

Scan this text and follow the final link for a series of scientific papers on the natural history of the Royal National Park.

“The Linnean Society was founded in 1788 by botanist Sir James Edward Smith. The society derives its name from the Swedish naturalist Carolus Linnaeus, the ‘father of taxonomy’, who systematised biological classification through his binomial nomenclature. He was known as Carl von Linné after his ennoblement, hence the spelling ‘Linnean’, rather than ‘Linnaean’. The society had a number of minor name variations before it gained its Royal Charter on 26 March 1802, when the name became fixed as “The Linnean Society of London”. In 1802, as a newly incorporated society, it comprised 228 fellows. It is the oldest extant natural history society in the world. Throughout its history the society has been a non-political and non-sectarian institution, existing solely for the furtherance of natural history” Gage A.T. and Stearn W.T. (1988) A Bicentenary History of the Linnean Society of London, Linnean Society of London, p. 148

The Linnean Society of NSW

FOUNDED 1874. INCORPORATED 1884. ‘NATURAL HISTORY IN ALL ITS BRANCHES.’

Natural History of the First National Park

A Symposium presented by the Linnean Society of NSW and National Parks & Wildlife Service was held in the Auditorium of the Visitor Centre, Kamay Botany Bay National Park 29 September – 1 October 2011.

For a list of talks and posters presented:

http://linneansocietynsw.org.au/symposia/First%20National%20Park/First_National_Park.html

For pdf files of the published proceedings:

https://openjournals.library.sydney.edu.au/index.php/LIN/issue/view/470

I can promise you maps and pictures of roadkill.

Rays, they have their ways

Having the use of a photographic drone opens up possibilities for good not evil. What could be healthier than counting animals for the greater good? Can I just say no migratory birds were distressed in the making of these images and no people were given cause to panic. The shots were taken in the early morning light with the sun low in the east casting long shadows across the water. The tiny tadpole creatures you see in the picture are in fact fiddler rays which are usually under a metre in length. By comparing two photographs taken sequentially of the same spot it is easy to see them move about. No doubt there were some rays in this photo who were moving too slowly to be observed or still hidden in the seagrass. Would I be making a wild guess to suggest that there are dozens of fiddler rays in the larger context? Possible hundreds?

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The mysterious multitude of holes

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Mangrove root zone – holding back the holes

The sand flats of Deeban Spit resembles a lunar landscape pockmarked with craters. All agree that they are a sign of life, but there is some mystery as to which form of life is active here.  There are the obvious human makers of holes who descend on a fine fishing day to pump bait from the sand. They carry a stainless steel cylinder to jab into the wet sand and extract a core of sand which is then dumped on the surface for inspection. The fisher person is only interested in finding nippers, the ghost shrimp Trypaea australiensis. The nipper is a bountiful little crustacean that is a natural food source for estuarine fish and makes good live bait. Research done here in 2004 estimated that 4500 nippers are extracted from the sand in Maianbar on a typical weekend day in summer. That is a lot of nippers and a lot of holes made in the sand. The good news is that despite the pumping less than 2% of the total stock of nippers are removed by bait pumping. (Rotherham 2004) And yet this does not explain the vast bulk of holes in the sand. The sand is like a whiteboard, each incoming tide goes some way to erasing the marks made before. Holes made last summer may be hard to find. Depending on the strength of the current and the action of the water all holes will be filled and levelled in time. Yet new holes appear, thousands of holes, even when there is no fishing and pumping for bait. Fresh holes appear in the winter when a fisher person is not seen for weeks. Other life is obviously at work.

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Fishermans Bay looking south along Yenabilli Point

If I was to begin my life again as a student in search of serious study I could do worse than measure all the holes on Deeban Spit.  Each imprint in the sand is a sign of life that communicates some activity. The sand reveals an interactive pattern of movement, of feeding, of hunting and hiding. The traces in the sand can be deciphered and the holes would be the basis of this study.

At the outset I would probably try to save myself some effort by finding a system to sample the holes, then I could avoid measuring every single hole and extrapolate answers from a limited study. This need to form an answer by sampling is central to scientific research of all kinds and is in itself a science, call it statistics. If the entire sandflat is one uniform canvas evenly covered in holes it would be easy to sample, a study of one small area could be scaled by multiplication to arrive at an answer for the whole area. This would be too simple and no fun at all. The real world is rarely uniform and patterns of all types are recognisable. Perhaps the most useful pattern in statistical studies is the idea of the random pattern, where there is no particular order in things. In physics this might be compared to entropy and the famous second law of thermodynamics in which the universe winds down to a bland nothing-much-happening-here lifeless energy-free state. Life itself is a system of order and living things are not often following random paths. And so we can use the random concept as a tool to measure living systems. By comparing measurements taken from the real world to random patterns we can assess whether there is some order that needs investigation. This is the basis of fundamental statistical models, is there a variation in the real numbers that differs from a hypothetical random set of numbers? If you can believe this then you can believe in science as it is practiced today.

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Incoming tide erasing fresh holes. Whelks emerging to feed.

Back to the holes.

Some guesswork

1/  I think the holes would fall into size categories – there would not be a random pattern of holes from pinprick sized to the size of Fishermans bay itself. There would be clusters of holes that conform to different types of animals. The burrows of nippers would cluster around one range of sizes and the holes of soldier crabs would cluster around another range of sizes. All the animals that make an imprint in the sand would leave a set of holes that would form groups of numbers that are not random. There may be overlap between different animals, but there would be distinct size classes.

2/ The distribution of the holes across the landscape would not be random. Different animals have different ranges and so we would not expect to find evidence of all animals in all places. We would expect to find clusters of holes in different zones of the environment.

These two simple expectations form the basis of ecological study; the abundance and distribution of life. But a theoretical framework is complimented by the simple act of observation. I have seen animals make similar marks to these and so I believe that these marks are made in a similar way. A little faith is always necessary.

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Holes of one size class are easy to count – 25 (give or take)

 

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100 stingray-sized holes (but are they all made by stingrays?)

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500 holes

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10 000 holes

 

 

The dead ugly Dolabella auricularia

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The sea slugs, or nudibranchs, include some beautifully frilled and coloured characters, Dolabella, the Sea Hare, is not one of them. Even when alive and looking at its best it has the mottled lumpy look of decay, they are well camouflaged for a life  hidden in amongst the weed. It will make itself known if you accidentally stand on it and it releases a tell-tale reddish purple  “ink”. When they wash up on the beach, after a storm perhaps, the dead Dolabella shrink and dry and their inner ear-shaped shell will split the body from within.

The beached carcass reveals the basic anatomical plan.  At the anterior end there is a pair of tentacular feelers at the mouth and a pair of club-like chemosensory rhinophores set further back. No eyes as such. Sea slugs are hermaphrodites, with a long stalked penis housed inside the head and a female opening to the rear. The penis is seen here as a lump on the right hand side of the head, it connects by an exterior groove to the inhaling siphon, seen here with shell protruding. When mating the sperm travel up the groove to the penis. Water taken into the enclosed mantle cavity is expelled through another siphon in the middle of the basal disc. The gut also empties into this mantle cavity and excreta and ink are all expelled through the posterior siphon.

Dolabella can grow up to 400 mm in length and they make a living as browsing herbivores feeding mainly on macroscopic algae. Like all molluscs the sea slug has highly modified mouthparts, developed here as a radula, which resembles a tiny chainsaw.  The diet of plant material is based on a preference for softer tissues, so the tougher calcareous seagrass blades will be stripped clean of softer filamentous algal growth. These sea slugs may be grooming the seagrass beds and restoring photosynthetic function in  polluted waters where excess nitrogen has resulted in abundant algal growth.

If cleaning the seagrass is not enough to earn our admiration, it seems this species of sea slug can also cure cancer. From its varied diet the animal stores various anti-mitotic chemicals which are used to suppress tumour growth in cancer patients.  And of course the Dolabella and its long filamentous egg mass are edible, apparently semi-cooked with vinegar. Hopefully they escape the notice of local gourmands.

For anyone interested in going down the rabbit hole of sea-slug taxonomy there is forum group seaslugforum.net. This is possibly the best organised forum group I have EVER seen. Photos, description, Q&A, lists of scientific references. Just for a laugh check out the extensive species list, our little seaslug Dolabella auricularia is placed partway down the list under FAMILY Aplysiidae, which is under SUPERFAMILY APLYSIOIDEA, which is under ORDER ANASPIDEA – Alternatively, rather than searching blindly, use the find function on your computer – command+F for macs, or control+F for PC. http://www.seaslugforum.net/specieslist.htm

Noisy Racist Tweets

noisy-tweets

In Maianbar there is an over-abundance of parrots,  Sulphur crested Cockatoos, Rainbow Lorikeets, King Parrots and the odd Little Corella and Crimson Rosella. These are the species that have learned to exploit the kinder nature of nature-loving people, they beg and steal and sing for food handouts. The birds are adaptable and will take seed or bread or fruit or any unattended pet food. Cockatoos will try almost anything, even flying off with a greasy bone. The nectar feeding lorikeets  will take seed perhaps doing damage to the fine bristles on the tongue that would normally brush the nectar from flowers. The King parrots take the last place in line as they have none of the unruly aggression of the others, but since they have the most beautiful plumage and melodious song the people will see that  they are fed.

Where food is plentiful there is overcrowding and competition for nesting hollows. An unhealthy diet and cramped living leads to disease and many of the cockatoos show the symptoms of beak and feather disease, where the feathers fall away and the beak elongates into an awkward hook. Young birds are particularly susceptible to the disease and are often evicted from the nest with the onset of disease. The cockatoos are relatively recent arrivals to the coast, they have come from the inland in a migration following the resources we have made available. Birds that are common in cities and suburbs and in the rural landscape are often there because of the food and shelter we provide. Like people, the birds that thrive in our suburbs are also colonists. Operating in large social groups these birds are able to set up a co-operative arrangement where competition from other species is squashed.

Early in the Maianbar morning before the dawn, about the time of the first Kookaburra call there is a high pitched soft piping chorus of birds calling. These are the Noisy Miners, a native bird that has spread with the suburban garden and the popularity of the sticky nursery trade grevillea flowers. During the day the Noisy Miners give voice to a wide range of calls, keeping a buzzing social scene that is more about alarm than attraction. Other small birds are commonly chased out of the gardens, and the miners are  given to violent territorial squabbles between themselves.

Each of these birds adapted to suburban life has a similar cousin who remains in the wild. The brash white Sulphur crested Cockatoo has a shy black twin, the Yellow tailed black Cockatoo, a bird that is less ebuliant and almost secretive. The   Rainbow Lorikeet has perhaps taken the place of the Eastern Rosella a bird that was once common while suburban developments still had outskirts of scrub and meadows of seed bearing grasses. The Noisy Miner has interestingly pushed ahead of the  introduced Indian Mynah that was once dominant in the Sydney suburbs. The Bell Miner is also on the upsurge and is thought to be responsible for the spread of Eucalypt die-back, through its displacement of pest controlling bird species.

One other pair of songbirds that should be more common inside the suburban setting of Maianbar is the Superb Fairy-wren and the Variegated Fairy-wren. These birds do well when a little of the low shrub lawyer is left intact and cats are not free-ranging. In these birds the family group work together as a small tribe eating insects. In both species all the birds are drab except for  the adult males which stand out with an electric blue cap, nape and cheeks. In the Variegated Fairy-wren the blue  of the mature male is augmented with little chestnut shoulders. The calls of both species are also very similar in structure but they are noticeably different.

And now for the racism. Birds of the the same species, that is birds that are able to produce fertile offspring, are often separated geographically, by a barrier or an area of unsuitable terrain, and since the separated groups are not interbreeding they develop slight genetic or cultural differences. These diverging groups are described as different races of the same species. Over time the drift in the differences between separated populations  may ultimately lead to the development of separate species. One of the key drivers of this separation is the development of bird calls, a cultural shift that leads to speciation through sexual selection. There is a natural diversity in the song patterns that may be inherited, but song is also coloured by mimicry. Other birds may lend elements to the repertoire. The attraction of a newly developed call replaces the attraction of the old call.  And so it is that the choice of a  suitable candidate for reproduction is linked to the development of noisy racist tweets.

Sunset on the Fan Shell?

Here lies the remains of the last Fan shell on Deeban Spit.

Possibly.

Over the last two years the number of Fan shells poking out of the sea grass on Deeban Spit at low tide has plummeted. Where once there was a field of a thousand gaping shells, there are now almost none, and those that do remain are empty.

I miss them.

Empty shells on oyster beds

Fan shells are known locally by the more dramatic, but incorrect name of Razor clams. Yet another animal menace just waiting to extract human blood. They are popular in recipes of an Asian flavour, put “razor clam” in your search engine and cooking pops up first, but you will notice that true Razor clams look like old-school cut-throat razors, while our Fan shells look like fans, or perhaps the ear of a donkey. They are all edible regardless of name.

The big shells out on Deeban Spit  are  Pinna bicolour, bivalve molluscs in the genus Pinna, latin for ear. Pinna bicolour is a widely distributed species named for the bright iridescence of the inner shell. It is restricted to the sandy seagrass beds where the larvae are able to settle and feed. Research done in the warm waters of Malasia and the cooler waters of South Australia shows that they grow quickly and reach 20cm in length in the first year. By the second year they reach 26 cm and they are full size in the third year at 35 cm. Lucky Fan shells may go on to live well over a decade, the old ones gather epibiota, just like the hull of a boat.  Eventually they get tired, weighed down and stop moving. Where the seagrass beds remain there is a good chance the Fan Shells will return.

live fan shell survivor
empty fields empty fields

The carnivorous Moon Shell egg mass

Often claimed to be shark poo, these gelatinous croissants made of mucus and a sprinkle of sand are in fact masses of eggs laid by the Moon Shell, a carnivorous snail that feeds on other shelled molluscs. On the sand flats the molluscs include the oysters seen in the photo and the whelks that lie around casually waiting for the returning tide.

If you are a keen observer of sea shells on the sand you will have noticed that some types of empty shells have a tiny neat hole usually drilled at the apex, in the ideal place for threading a necklace. The molluscs that produce these shells have a pair of shells that come together to form a shelter for the soft innards, they are known as bi-valves. The mollusc that made the hole is another type entirely, a gastropod – like the garden snail. The class Gastropoda contains a vast total of named species, second only to the insects in overall number. Moon shell gastropods are able to travel along quite efficiently by extending a big muscular foot. These active mollusc are then able to hunt the less agile bi-valves and anything else that they come across. Moon shells can be carnivorous and they are also known to feed on soldier crabs.

Molluscs have a body plan that  incorporates hardened elements, usually a shell, in the case of an octopus it is a horny beak, while gastropods have a shell and a radula, a tongue structure that looks like a miniature chainsaw composed of many tiny teeth on a band that will easily saw through plant material or drill holes into shells. The moon shell will grab hold of the prey with its foot and locate the precise spot to start drilling with the aid of an acid secretion, the muscle that clamps the two shells together is disabled and the shells can then be prised open and the contents removed.

The moon shell that is commonly found on the Deeban Spit is Polinices (Conuber) sordidus

There is an illegal market for shells collected in Port Hacking with specimens selling for $10 each.

Flannel Flowers

Actinotus hellianthi, the larger of the two Flannel flowers. The larger flowers seem to require more light and are found in exposed positions on rock platforms and on the roadside, while the smaller flowers of Actinotus minor are more common and grow twining through other shrubs and ground cover.

Notice many small black beetles active in the middle of the flowers, probably feeding and acting as pollinators.

Flannel flowers are part of the Apiaceae family and are not daisies, but like daisies the flower structure is not straightforward. In Flannel flowers the centre of the flower is composed of many small florets while the outer rays are actually bracts not petals. The name Actinotus comes from the Greek aktin-/ακτιν, meaning “ray” or “spoke of a wheel” or “sunbeam”.

This group of flowers is growing on the bush track alongside Maianbar Drive overlooking the Basin.

For the big picture click below.

flannekl Flower

Recent Reference Material

Anyone interested in the geography of Port Hacking will enjoy reading this report on disc, available free at the reception desk at Sutherland Shire Council chambers. The disk contains a massive trove of historical photos and views of the natural features of Port Hacking and the catchment area, including the Royal National Park. Of particular interest is the thorough research into the movement of sand and the history of dredging on Deeban Spit.

To see the written section of the report click on this link:

Port Hacking – Past and Present of an Estuarine Environment

The work was released in February 2014 and represents a synthesis of three decades of work by A/Prof Alberto Albani of UNSW and George Cotis, a long time activist and friend of the Hacking. Both authors have extensive experience in the management of coastal regions and  estuaries. Highly recommended.

Snakes and Ladders

The Green Tree Snake is an occasional ground dweller, and when disturbed on the ground it seeks refuge by climbing.  This little snake climbed up a broom handle only to find a dead end.  Now seen back down onto a brick wall and seeking a better  route to the treetops. The Green Tree Snake, Derendrelaphis punctulata,*  is one of four species found in our backyard – all of them are harmless to people.

For the big picture click below.

green tree snake

*Dendra – latin for tree, Elaphe – are another genus of snake, punctulata – fine spotted

http://www.arod.com.au/arod/reptilia/Squamata/Colubridae/Dendrelaphis/punctulatus

Dirty Lizards

There are two distinctly coloured populations of Eastern water dragons living in this corner of Fisherman’s Bay. There are the clean dragons living in the back yard and then there are the dirty dragons that live down by the creek. Clean dragons are grey, flecked with black and white, and dominant males have a distinct red blush on the chest. The rusty dragons live in creek water which carries iron tinged algae. The colour is permanent, but because lizards shed shed their skin a dirty lizard will eventually become clean if it moves away from the creek. The change of colour will take a couple of years to be complete. Some lizards will carry a two-tone appearance for some time.

All dragons like to slumber on a warm patch of their territory. This group of three females and a larger male are taking advantage of a clearing in the ferns where the sun heats the dark soil by the creek. These lizards have been swimming and are now mostly dry, but there is wet patch where one female lizard has been lying on top of the male in the middle. The male can be identified  by his large head. Males wrestle to gain dominance, so there is an advantage to having a large head, or rather, a larger set of jaws.

Which brings us to the latin name of the water dragon; Physignathus lesueurii, where the generic epithet (the first capitalised part of the binomial) refers to a large jaw. The specific epithet refers here to the French artist and naturalist Charles Alexandre Lesueur who traveled with Baudin to Australia in 1801. The Baudin expedition collected over 100000 specimens and many  animals were described from this collection.

Powerful Pellets

Looking up through a skylight I wondered about the large grey sausage adhered to the glass. Some days or perhaps weeks later I went up on the roof and discovered the best part of a small skeleton encased in a tight felt cocoon. On opening the package a pair of mandibles appeared and from the dentition I was able to identify the remains of a brush tail possum. Only one animal will eat a possum and drop the remains in the form of a pellet; the Powerful Owl, Ninox strenua

The pellet is the indigestible portion of a possum meal and it was coughed up from a roost in the Angophora tree that grows over our house. In the following months I found gizzards dropped on the roadway and later the dismembered wings of a fruit bat.

At night in the winter, more often after rain, the Powerful Owl can be heard calling. Locals have different theories about where the owls may nest, roost and hunt. Perhaps they are occasional visitors, perhaps we share a pair with Bundeena.

The powerful owl is listed as a vulnerable species due mainly to habitat clearing. We are fortunate indeed to have them here in Maianbar

To hear a recording of a Powerful Owl calling click on this soundcloud link

The Beginning

This is the first post to the newsfeed. Fresh posts will displace older posts from the top of the page. It is also possible to make the home page static so that the visitor is met with an introduction, but more often this is included in a page titled About because returning visitors would prefer to see something fresh. To keep a post at the top of the page it can be made sticky and it will then cary the Featured title

Scroll down the home page and the posts will appear in sequential order, a quick way for people to catch up on content

To the left hand side are all the widgets and  there are many choose from. I have opted to stack the sidebar with links to static pages – including index of contents and a page introducing myself, and another page for references – Like the posts these pages can have room for comment by visitors, or not. Readers love to leave comments and often the sidebar is used to reward comments by listing latest comments. The engagement of readers is the main way of generating traffic.

All comment can be published immediately, or subject to approval.

The sidebar also include a tag cloud that ranks the tags by size according to the number of entries.

When exploring the site the reader can reset the journey by returning to the top of the home page called up by pressing the title of the sidebar; ecology of MAIANBAR

At the foot of posts are tags and categories, these can be used to draw up all pages on Botany (a category) or more specifically all pages on a particular plant or flower colour (a tag). All content contains  links that may lead to other outside content or to further expansion of text or images, usually such links are underlined, except in the case of an image where a note is given.

Enjoy