Burn-off at Bujwa Bay

The only trouble with living in paradise (apart from the long commute) is combustibility.  Our gorgeous view – mile after mile of incendiary eucalypts.  So the still, dry days and nights of autumn were thick with smoke, not from the big bad one we’re dreading, but hazard reduction burns in the bush all round the town.

Last time I went down to Bujwa Bay, it was the kind of cool and breathless day that must make the Rural Fire Service very very happy.   Mist hovered over the water in a bright line of morning light.  Forty minutes of silent paddling past the sleeping celebrities of Berowra Waters and I was round Oaky Corner and into the sunshine.

In the quiet there was a cryptic crunching noise.   Eventually, I spotted the pair of glossy black-cockatoos hidden amongst at the shore-line casuarinas.  My sense of being some kind of bird whisperer evaporated when, after fifteen minutes fooling around trying to get a decent shot of the cockies, I looked up to meet the eye of a bloody great big white-bellied sea eagle sitting directly above me.  And then, just round the corner, his pal taking in the rays.  They’re not stupid these birds, parked in the sunniest spot on the bay.

Having bonded with the local bird-life, when I heard about the burn-off, I was worried.   What happens to it all when the bush goes up in smoke?

Bujwa bay wide view 2 best small

Egg the kayak entering Bujwa Bay after the burn-off

Drooping bark and grasstrees for crop square

Back-burnt grasstrees at Bujwa Bay

It’s not all bad news.

Harry Rechter describes  birds enjoying a feast during a controlled burn in Brisbane Waters National Park, not so far from here.
“Although fuel loads in the… heath and woodland were high, and flames soared above the tallest trees and shrubs, birds moved easily in front of and above the fire to appear minutes later on the blackened vegetation to feed on less fortunate insects and small lizards”.
I missed the raptors and the insectivores that no doubt turned up at Bujwa Bay at the first sign of smoke, looking for Cajun-style chow. But chances are these blackened grasstrees will be bursting into flower next time I paddle by.  I might see lyrebirds too, raking newly formed clearings.  Ground-feeders and grain-eaters – corellas for instance – return in force after fires have passed.  The little insectivores – thornbills, wrens and robins – that build nests close to the ground don’t miss the scorched canopy, and enjoy the bugs that flourish on the flush of new growth.  The carbonised shrubbery might even give me the chance of catching a blurry LBB or two on film.
Burnt crown and cliff

After the burn-off: partly scorched eucalypts

It’s a nice idea to think that the burn-offs that protect the town are a boon for the local plants and animals too.   And there’s a euphonious catchphrase that goes with that idea: “pyrodiversity begets biodiversity”. Fire incinerates the garden escapes and wakes the soilbank’s astounding store of dormant seeds. If we burn little and often, it’s been thought, we make a mosaic of habitats: patches of open space and newly germinating seeds; places burnt a few years back; and refuges long unburnt, full of craggy trees, hollow logs and dense undergrowth.

Pyrodiversity is popular amongst land management folks, and there’s some evidence that it works, at least in some places.  But not everyone buys the story that the frequent fires that protect people and property suit other critters too. Out in the mallee, near where I grew up, a fire and biodiversity project run by Deakin and LaTrobe universities has been laboriously checking the idea out.

For all the mallee’s underground lignotubers, ready to reshoot after fire, other parts of the ecosystem – large stretches of spinifex grass, for one, that shelter dragons and legless lizards – can take fifty or more years to return after a burn.  All of which makes me feel tremendously guilty about the swiftly abandoned spinifex-covered cubbies that my brother and sister and I used to make in the mallee scrub out the back of our house.  We will never know how many now-extinct species we displaced.

Away from regrets about the trail of ecological devastation I left in childhood and back to burn-off related angst. The research in these arid areas suggests it’s not pyrodiversity that’s important for a species-rich environment but having enough country that’s reached the right stage of maturity since the last fire.  As a person in mid-life, it pleases me to say that older vegetation often seems to sustain more species of birds, mammals and reptiles, including the rare ones. Even birds that like paddocks and open plains prefer unburnt land.  Some reptiles favour recently fired landscapes, but plant communities that haven’t been burnt for a decade or two harbor the richest variety of lizards and snakes.

I tried and failed to find the experts on biodiversity and fire on Hawkesbury sandstone.  But researchers studying both subtropical Queensland and foothill forests in Victoria said similar things.  A varied landscape is important, but

the richness of frugivore, insectivore and canopy forager assemblages is driven by the presence of structurally complex vegetation and old-growth canopy trees, which are more likely to be present in areas that have not experienced fire for a prolonged period of time (Burgess 2016)

Paston and colleagues put their conclusion bluntly: “prescribed fire is of little utility for the broadscale conservation of biodiversity” (2011, 3238).

And it seems, for birds at least, smaller patches of unburnt country won’t really do – it’s larger areas that haven’t seen fire for a while that are rich in species.  One bunch of researchers found that little islands of older habitat surrounded by new growth was grabbed by one or two aggressive predatory or colonial birds, rather than harbouring lots of different critters.  One recent paper, written about arid areas, sum it up:

Our results suggest a shift in current fire management thinking… is needed, away from a focus on creating small, unburnt patches towards preserving large, intact, unburnt areas (Berry 2015 493)

Burnt crown and dark silhouette from distance

What does all this mean for Bujwa Bay?

There was nothing moving in the incinerated trees on the ridgeline as I made my way up the creek at high tide, but then, it was early and damn chilly.  Even the herons had given up on fishing and were huddled in the trees, keeping their feet dry.

But the damp fringes of the mangroves were alive with silvereyes and yellow-faced honeyeaters, and I heard the plunk of a sacred kingfisher diving for breakfast.  Gullies are especially valuable habitats for birds at the best of times.  If they’re protected from fire by burning on the slopes nearby they can be an even better retreat when that big one comes.  The top of the creek was lush and green. I can only guess that the rangers and RFS know what they’re doing.

White faced heron in tree 2 square

Chilly looking white-faced heron

In the light of recent research, Taylor and his colleagues comment dryly “current fire management for avifaunal conservation may require substantial refinement” (Taylor, 2012, 525).

But let’s not fool ourselves.  Around here at least, fire management is not for the avifauna.  It’s for me, and people like me, who choose to live high on a hill, surrounded by the beautiful, burnable bush.

Additional references.  Because the whole thing is really is quite complicated and you might want to check I didn’t get it totally wrong.

Berry, L. Lindenmeyer, D, Driscoll, D. (2015) “Large unburnt areas, not small unburnt patches, are needed to conserve avian diversity in fire-prone landscapes” Journal ofApplied Ecology Vol 52 Issue 2

Burgess, Emma, and Maron, Martine (2016) “Does the response of bird assemblages to fire mosaic properties vary among spatial scales and foraging guilds?” Landscape Ecology March 2016, Volume 31, Issue 3,pp 687–699

Doty, A., Stawski, C, Nowack, J., Bondarenco, A. (2015) “Increased lyrebird presence in a post-fire landscape” Australian Journal of Zoology 63,9–11

Hope Ben (2012) “Short-term response of the long-nosed bandicoot, Perameles nasuta, and the southern brown bandicoot, Isoodon obesulus obesulus, to low-intensity prescribed fire in heathland vegetation” Wildlife Research 39(8) 731-744

Korczynskyj, Luke and Byron B. Lamont (2005) “Grasstree (Xanthorrhoea preissii) recovery after fire in two seasons and habitats” Australian Journal of Botany, 53 509-515

Kelly, Luke T. Andrew F. Bennett, Michael F. Clarke, and Michael A. McCarthy (2015) “Optimal fire histories for biodiversity conservationConservation Biology, Volume 29, No. 2, 473–485

Lindenmayer, David B., Wade Blanchard, Lachlan McBurney, David Blair, Sam C. Banks, Don A. Driscoll, Annabel L. Smith and A. M. Gill (2014) “Complex responses of birds to landscape-level fire extent, fire severity and environmental driversDiversity and Distributions 20, 467–477

Nimmo, D, Kelly, L., Spence-Bailey, L, Watson, S.J. Taylor, R.S., Clarke, M.F and Bennett, A.F. (2012) “Fire Mosaics and Reptile Conservation in a Fire-Prone Region” Conservation Biology 27 (12)

Pastro, Louise L., Christopher R. Dickman and Mike Letnic (2011) “Burning for biodiversity or burning biodiversity? Prescribed burn vs. wildfire impacts on plants, lizards and mammals”  Ecological Applications Vol. 21, No. 8, pp. 3

Robinson, Natasha, Leonard, Steven, Bennett, Andrew, Clarke, Michael (2016) “Are forest gullies refuges for birds when burnt? The value of topographical heterogeneity to avian diversity in a fire-prone landscape” Biological Conservation 200, pp.1-7

Sitters, Holly , Di Stefano, Julian, Christie, Fiona, Swan, Matthew, York, Alan (2016) “Bird functional diversity decreases with time since disturbance” Ecological Applications, 26(1), pp. 115–127

Smith, Annabel, C.Michael Bull, Don Driscoll (2013) “Successional specialization in a reptile community cautions against widespread planned burning and complete fire suppression”Journal of Applied Ecology 2013, 50, 1178–118

In praise of sewage

“Cockle Creek? Ooo, I wouldn’t put in there” my sister’s mate, the local, said “They’ve been dumping heavy metals in that spot for years! And there’s the sewage farm up the river as well.  I’d steer well clear”.

I muttered to my sister as we walked away “What do you think? Are you worried about heavy metals and sewage?”

“Nah!  Let’s do it!”

Sunrise on Lake Macquarie

Sunrise on Lake Macquarie

The power of poo.  Over the last couple of years, I’ve been hearing a lot about it from my fabulous friend and colleague, Cath Simpson, at this very minute writing a documentary for Radio National full of plops and splashes.

Thanks to some bad experiences with cholera and typhoid, we modern city dwellers generally a bit iffy about human excrement. But the bacteria that dwell in and on us – our own personal ecosystems – seem to be quite critical to human health.   While I’m a huge fan of the toilet, poo is not all bad.  If you have a nasty case of Clostridium difficile, for instance – an infection that kills 30,000 Americans every year, often older people in hospitals who have had their bacterial ecosystems depopulated by antibiotics – a “faecal transplant” from a healthy donor is might well be your best chance of a cure.

If the much of Western world, with its convenient superphosphate fertiliser and cow-pat free central heating, has been a bit “ew” about excrement, one sub-culture has held the faith.  Bird watchers have never lost confidence in the value of ordure.

Cormorant diving crop for trim

Painterly pied cormorant fishing in Lake Macquarie

When Birdlife Australia asks “where’s your favourite birdwatching spot?”, do you choose an offshore island, fringed with white sand?  the lush splendour of the tropical rainforest?  Or choice number three, a sewage treatment plant? And you guessed it, the first comment is a ringing endorsement of the glories of the Alice Springs Sewage Ponds.

So I wasn’t really surprised at the new and exciting birdlife I saw up  Cockle Creek in amongst the drowned computer monitors, abandoned bridge footings and Impressionist riverscapes subtly enhanced by a discreet discarded tyre.

So many striated herons I got bored of taking photos.  White-cheeked honeyeaters.  Orioles.  Black faced cuckoo shrikes. White breasted woodswallows, showing off their 80s batwing styling.   Double-banded finches with their neat dress shirts, black ties and cummerbunds.

Why are sewage treatment plants so great for birds?  Well, wetlands are a particularly threatened habitat – a third of Victoria’s wetlands have been drained over the last two hundred years, for instance – and old-style sewage ponds offer alternative places for birds to feed and rest, especially during droughts.  With plenty of nutrients, the settling ponds of sewage treatment plants actually offer more invertebrate snacks than natural wetlands, and sustain a greater range birds. Christopher Murray’s research in Victoria has found that newer treatment plants – the dynamic sounding “activated sludge” facilities – that take up less expensive real estate than old-fashioned waste stabilisation ponds (and smell better) are less appealing from a waterbird’s point of view.

If the news on sewage plants is pretty good, I’m not so sure about the heavy metals. Cockle Creek really has been a dumping ground for cadmium and lead, among other things, from the smelter in Boolaroo, on and off for more than a century.  There’s black slag from the plant tucked away in all sorts of unexpected places around the lake shore and lead, zinc, mercury and cadmium lurk in the creek’s sediment, 70 centimetres deep.

The smelter closed down in the noughties and the site is still being “remediated” for housing.  Previous “abatement” strategies seemed to involve scraping off a few centimetres of topsoil and (after most of the local pre-schoolers were found to have worryingly high levels of lead in their blood) urging kids to  “Wash wipe and scrape – you’ll be right mate!”. In the 1980s and early 1990s, the streets closest to the “The Sulphide” were rented out on the strict condition that the household should have no children or pets.

There’s a giant Bunnings there already, though, amidst the rubble.  Perhaps the logic is that the visiting DIYers are heading home to put a mallet through an asbestos wall, so where’s the harm in throwing in a spot of bonus lead?

The local birds seem to be doing okay, though.  A pair of ospreys nest at the top of a Norfolk pine at Speers Point, where Cockle Creek flows into Lake Macquarie, and this last year they’ve had chicks.  Osprey are locavores and since they’re at the top of the food chain, anything toxic in the fish they eat ends up in their chicks.  Eventually.  It takes a while for our endlessly updated array of contaminants – from DDT to teflon, fire retardants and hypertension medications – to make it into the bloodstream of the baby raptors.

Osprey wings bent crop wide

Osprey with fish at Speers Point, Lake Macquarie

I’ll be back to Cockle Creek for sure, to see what the local sewage has in store for me.  Trying to tread lightly, and hoping not to feel too much lead and mercury squelching between my toes…

D in canoe at dawn small more waterReferences

Murray, C. G. & Hamilton, A. J. (2010). Perspectives on wastewater treatment wetlands and waterbird conservation. Journal of Applied Ecology, 47(5), 976–985. DOI: 10.1111/j.1365-2664.2010.01853.x

Murray, C. G., Loyn, R. H., Kasel, S., Hepworth, G., Stamation, K. & Hamilton, A. J. (2012). What can a database compiled over 22 years tell us about the use of different types of wetlands by waterfowl in south-eastern Australian summers? Emu: Austral Ornithology, 112(3), 209–217. DOI: 10.1071/MU11070

Murray, C. G., Kasel, S., Szantyr, E., Barratt, R. & Hamilton, A. J. (2013). Waterbird use of different treatment stages in waste-stabilisation pond systems. Emu: Austral Ornithology. DOI: 10.1071/MU12121

Murray, C. G. & Hamilton, A. J. (2012). Sewage ponds a refuge for wetland-deprived birds. ECOS, 175. http://www.ecosmagazine.com/?paper=EC12418

Encounters with eagles

May I present this week’s sea eagle?

As yet on my estuarine adventures, I haven’t seen a score of sea-eagles on a single morning (although I can imagine a battalion of them, flying in formation), but an encounter with an eagle has become as much a regular feature of my kayaking expeditions as the ubiquitous white-faced heron. Those cryptic little passerines in the riverside scrub are hard to spot even if you’re not short sighted and half deaf.  So three cheers for the white-bellied sea eagle “large and conspicuous” “easily sighted when… soaring… in search of prey“.  Haliaeetus leucogaster, you are the middle aged canoeist’s friend.

There was the eagle we saw battling it out with a pair of whistling kites over fishing rights on a fabulous family excursion across the Hawkesbury from Brooklyn, across the surf-line and up the Patonga River.  According to Wikipedia, sea eagles harass smaller raptors like kites in hopes of stealing their prey.  Not today, Josephine.  This eagle was bested by the lowly kite, unwilling to relinquish a top notch fishing spot.  I need to listen to my own advice to my students – don’t believe Wikipedia!

An eagle even made a guest appearance on a modest little paddle down the end of our street.  This was one mellow raptor, its apparent indifference to poorly coordinated amateur photographers splashing around trying to get a good shot belying its rep as a “shy and easily disturbed species“.  Ruth, my companion on the water that day, had seen a sea eagle, earlier, on the very same bare branch, while bushwalking along the ridge above. Same bird or just a popular perch?

Since the rule for my stolen Saturday morning paddles is no more than half an hour in the car, I’ve frequently had this very thought as I spot yet another sea eagle.  Same bird?  Am I being stalked by just one glorious if persistent raptor who’s somehow taken a fancy to my little craft, charmed perhaps by its avian-friendly name?  Or is the Hawkesbury awash with sea eagles?

Even the Department of Environment in its definitive run down on Haliaeetus leucogaster doesn’t seem super sure. Their guesstimate of 500 pairs across the whole country is based on a one for every 40 kilometre of Australian coastline would pretty much mean that all the eagles in my photos are the same dude (or dudette – the females are larger but I find it’s kind of hard to tell if a bird is small or if it’s just far away).

Either way, I’m 100% sure this week’s eagle is a new one, since I saw it at the start of a paddle down Wallarah Creek, seventy ks north of here.  The creek wends its quiet way through bushland past the Wyong North sewage treatment plant to Budgewoi Lake.  What with my burgeoning interest in taking blurry pictures of distant bird-life, it seems I will be spending more and more time hanging around sewage farms – they seem to be the go-to venue for the would-be twitcher.

The Budgewoi eagles seem a bit more coy than the Berowra locals, as you can tell from this dodgy pic on my maxed out zoom.  Or maybe it’s just that this sea-eagle didn’t want to share her supersized snack.

Which, after observing the consequences of fraternisation with humans for other birds I saw on my way up Wallarah Creek, is probably a good thing.

Up until recently, it was thought that carelessly discarded bait, hooks and line were the big killers of waterbirds, and there have been some efforts made to make sure fisherfolk dispose of their scraps in the rubbish rather than leaving them lying around – not such a big ask really.  Some have even argued for the use of biodegradable line and hooks that will rust away (eventually).

But efforts to get fishermen to clean up their act have had surprisingly little impact on the number of waterbirds being injured or killed by fishing tackle.   In fact, research by academics and wildlife rescue organisations in South Australia and New South Wales suggest that the vast majority of birds that get entangled or hooked – often pelicans, but also plovers, gulls and stilts – get caught up when they are close to people actually fishing.

After my trip up Wallarah Creek I can see why.  As I passed riverfront houses with their landing slips and jetties I saw pelicans lounging on back lawns and an excited egret being thrown small fry by a local.  Even the striated heron, normally shy, flew off in the direction of human habitation, not the other way.  The birds around here are familiar with humans, their tinnies, their by-catch and, unfortunately, their fishing lines.

Broken Bay at low ebb

Last weekend I decided to explore the lower reaches of Mooney Mooney Creek from its meeting point with the Hawkesbury, riding on a rising tide. After my spooky solo paddles in Mangrove Creek, I had a hankering for the open horizon and a bit of human life around me. From my put-in at Deerubbin Reserve beside the freeway, and all the way round Spectacle Island, a nature reserve in the mouth of the creek, the constant hum of the traffic and the echoing rumble of trains crossing Brooklyn Bridge remind you that “civilisation” isn’t far away.

Low tide at Mooney Mooney Creek means mud and oyster leases.  The lingering blue haze from last week’s hazard reduction burns descended on the poles and frames, forlorn in the shallows, blurring them into beautiful abstracts.

The story of oyster farming in the Hawkesbury in recent times is a sad one, full of strange historical ironies.

People have been harvesting shellfish from the shores of the river for a very very long time and Sydney rock oyster has been farmed in Broken Bay since the 1880s.  In those days oysters were dredged from the estuary floor and after the meat was eaten, the shells, along with those from ancient middens, were burnt to make lime for mortar.

But in 2004, after a hundred years of farming oysters here, Qx disease hit the Hawkesbury.

The “Q” in the name stands for Queensland.  The Sunshine State produces a 10th of the oyster harvest it did in the nineteenth century, thanks to Qx and to the oyster-infesting mudworm (introduced from New Zealand in the 1880s along with imports of oyster spat). The “x” was a scientific shorthand for “what the hell is this anyway?  We really don’t know”.   Since then, researchers have figured out that Qx is caused by Marteilia sydneyi, a single-celled organism that during the summer infects oysters, causing them not just to slowly starve to death, but also to reabsorb their own gonads (nasty!).  The parasite then releases spores that cycle their way through a polychaete worm, Nephtys australiensis, in the winter, before reinfecting the oysters the following season.

M. sydneyi isn’t always the kiss of death.  The parasite is found in estuaries all along the coast of NSW and Queensland, even in “low risk” areas where Sydney rock oysters are still being commercially grown. Environmental stress, it seems, triggers outbreaks of Qx and surprisingly few wild Sydney rock oysters, the ones I saw lining the rocky shores of Mooney Mooney Creek, die from Qx. Which is good, if mysterious, news.

So, facing of losses of over 90% of the harvest, what could save the oyster industry in the Hawkesbury?

It was noxious pest to the rescue.

The Pacific oyster, farmed in Japan for centuries, was smuggled into Port Stephens in the eighties and spread quickly through the intertidal zones of New South Wales.  It’s a fecund and fast growing bivalve, planktonic eggs and larvae travelling far and wide, crowding, outgrowing, and sometimes settling on and smothering native rock oysters. A “selfish shellfish”, in the words of one inspired Tasmanian subeditor.

The very qualities that have made the Pacific oyster such a hateful invader came to the rescue of the Hawkesbury farmers in 2005.  A process for producing sterile “triploid” Pacific oysters had been developed in North America in the 1980s, with the aim of pumping out meatier shellfish fast. When fertility mean spawning 40 million eggs in a season (not to mention changing sex several times over a lifetime) avoiding reproduction saves a lot of energy.

Local farmers restocked with these “triploid” Pacific oysters.  As well as being immune to Qx, they were ready to harvest in less than two years compared to the three and a half years it takes rock oysters to reach the table.  The new “tamed” Pacific oysters took the Hawkesbury by storm.

And then in 2013 disease struck again. Millions of oysters were wiped out overnight by a virus that affected Pacific oysters and Pacific oysters alone.

Like the oyster itself, the scientifically spawned sterile “triploids”, and indeed the settlers that farm them, “oyster herpes” or POMS (Pacific Oyster Mortality Syndrome), first seen in France in the late noughties, had circled the globe to Broken Bay.

Only three oyster farming businesses are still going in the Hawkesbury these days, hanging on for scant supplies of Qx resistant rock oyster spat, first found amongst the survivors of the Georges’ River outbreak in the mid 1990s.

Right now, the derelict oyster farms are mostly places for posses of pied cormorants to hang out.

But there’s still plenty of life to be found at Mooney Mooney at low water: globe trotters like the eastern curlew, exhausted after a long flight south, and locals like the rock warbler that only lives on Sydney sandstone, compensating for its drab colours and homebody ways with a goth-style nest of grass and spider webs it hangs in the darkness of caves and crevices. And I clocked a new heron record – twenty at least, catching crabs in the mud of low tide.

References

Michael C Dove, John A Nell, Stephen Mcorrie and Wayne A O’Connor “Assessment of Qx and Winter Mortality Disease Resistance of Mass Selected Sydney Rock Oysters” Journal of Shellfish Research 32(3) 681-87 doi: http://dx.doi.org/10.2983/035.032.0309

Wayne A O’Connor and Michael C Dove “The changing face of Oyster Culture in New South Wales, Australia” Journal of Shellfish Research, Vol. 28, No. 4, 803–811, 2009.

J.A. Nell “The history of oyster farming in Australia” Marine Fisheries Review 63(3), 14-25

Nine herons hunting

Nine herons hunting… could it be the beginning of a carol for Christmas-in-July?  Not a bad sound track, perhaps, for a paddle on a wintry 25th down Mooney Mooney Creek.

There were (roundabout) eight cormorants, some of them cacking….

… three posing pelicans

… two eagles soaring

And a kingfisher in a mangrove tree (no photo, naturally).

But realistically, I could only get all the way through the twelve days of anti-Christmas by including the many invisible mud-loving animals that all those herons were stalking.  And I’m not quite sure if I have the alliterative and euphonious verbs to use for them.  Twelve isopods…. idling? Eleven worms a-wobbling? Ten crustaceans crawling?

Even if it can’t offer swans a-swimming or geese a-laying, Mooney Mooney does pretty well for both visible and invisible animals, considering how damn noisy it is.

I first started dreaming about paddling this creek as we swooped above it, across the lofty freeway bridge.  It’s a gorgeous structure, if you are partial to well-formed concrete: elegantly curved, arching vertiginously above the treetops of Brisbane Water National Park.  An endless stream of cars and semis cross the valley on the F1, the main route north from Sydney, on the tallest road bridge in Australia, the still water 75 metres below.

The Pacific Highway, looping its way down to its own modest crossing point, has plenty of traffic too: bikers switchbacking their way up the old road. This Saturday, I didn’t see a soul in three hours on the river, but for a mile or more I could hear the hiss of compression brakes and the revving of engines.

And yet, if I had to pick a place, of all the waterways I’ve paddled so far, to find and fail to take a picture of a kingfisher, this rowdy river is the one I’d choose.  The traffic noise seems to keep the humans at bay, but not the herons.  What’s going on with the wildlife around here?

There’s plenty of evidence that traffic noise bothers birds.  I particularly like a recent experiment where researchers planted speakers in a long line to create a phantom road.  That’s just what the freeway feels like from Mooney Mooney Creek – a road you can hear all over but mostly can’t quite see.  The phantom road, with its invisible traffic masking mating and alarm calls and the sound of approaching predators, cut numbers by a quarter, and drove two species away from the area entirely.

Some cope better than others.  High pitched songs are less likely to be blocked out by the roar of traffic, and so squeaky voiced birds are more likely to hang around in noisy places.  Species with a little vocal versatility often start to sing a bit higher, a little slower or in purer tones, just to be heard.

If you’re carnivorous, being able to hear the critters scuttling around in the bushes is a boon. Seeds and nectar are less likely to make a break for it, so background noise seems to be less of a big deal for the plant-eaters.  Also, birds that feed on the ground seem to mind the noise less – perhaps there’s more obstacles between them and the din.

Everyone agrees that in loud places, birds spend more time on the alert for predators – a high maintenance lifestyle.  That said, some nest-robbers are also put off by the rumble of traffic, so for some species, chicks hatching in noisy nests have a better chance of survival.  If you can handle the decibels, you may have a competitive advantage.

What does all this tell me about the plentiful birdlife of Mooney Mooney Creek?  Thinking about it, I saw high-pitched squeakers, mud-hugging stalkers and sharp-eyed hunters (see, I’m getting into the swing of this avian carol singing thing!)  I’m guessing striated herons don’t echolocate for crabs.  This white-faced pair were happy to ignore not just the distant thunder of trucks but the much more immediate annoyance of a nosy canoeist with a camera.

“The mud is like a Christmas tree”, my eight year old said, hearing the story of my low-tide adventures, “and the bird were excited to find all their presents”.

When the eating is this good, it seems, the soundtrack scarcely matters.

References

Francis, C.D. (2015) “Vocal traits and diet explain avian sensitivity to anthropogenic noise” Global Change Biology 21(5), 1809-1820

Francis, CD and Jesse R Barber (2013). A framework for understanding noise impacts on wildlife: an urgent conservation priority. Frontiers in Ecology and the Environment 11: 305–313. http://dx.doi.org/10.1890/120183

Francis, CD, Ortega, C and Cruz, A. (2009) “Noise Pollution changes avian communities and species interactions” (2009) Current Biology 19(16) pp.1415-19

Patricelli, Gail L. and Jessica L. Blickley (2006) “Avian communication in urban noise: causes and consequences of vocal adjustment” from The Auk 123(3): 639-49

Midwinter lagoon

It’s past the shortest day of the year, but, in spite of her scrapes and dings, Egg the elderly wooden kayak doesn’t seem to be ready for drydock yet.  Perhaps it’s that last unseasonable whirl of autumnal warmth, caught alongside the coast in the East Australian Current, that’s keeping the sea a balmy 20 degrees.  Or perhaps it’s just the lure of still, winter water all around.

Since Egg was first laid in our driveway a year ago, I’ve been seeing Sydney differently.   Those long roundabout routes from A to B via M and Q and P, punctuated somewhere along the way by a bridge or two, suddenly make sense.  The city of roads and buildings retreats and, I feel, just out of sight on every side, the presence of water.
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This is our backyard, encircled by the salty embrace of the Hawkesbury estuary.  But it doesn’t end here, with the secretive topography of flooded river valleys. All the way up (and down) the New South Wales coast, the shoreline is flanked by coastal lagoons. I’m not complaining, even the tiniest little bit, about all these sheltered waters.  But I’ve started to wonder what geographic accident has given a timid canoeist so much to feel grateful for.

Along with marshes and flats, coastal lagoons make up maybe 10% of the world’s seaboards, and in NSW lots of us live by them, many more than by the ocean itself. Lagoons (or wave-dominated estuaries – there are ongoing hissy-fits around these definitions) appear where low-lying plains, rather than dramatic cliffs, meet a shallow gently sloping seabed.  Usually, they are found on shores shaped mainly by waves rather than big tides, with underlying rock that crumbles nicely into beach sand not finer, silty sediment.

The more sand the better – perhaps our generous continental shelf harbours this bounty from a time when the Sydney Basin was a enormous braided river delta, like the Ganges today.  But you don’t want too much rain – lagoons are usually fed by an underwhelming little creek or even just groundwater – that doesn’t (or doesn’t often) burst through the land between waterway and ocean.

To make a lagoon*, you need a barrier to the open sea.  In the nineteenth and first part of the twentieth century, coastal geomorphologists duked it out over just how these barriers were born.  Did breaking waves make for ever-rising off-shore sand bars?  Did encroaching seas submerge coastal dunes? And then there’s the third, attractively named “spit accretion theory” (Davis and Fitzgerald, 2004).  Not, as it might sound, a creation myth where bunyips drool into puddles between the dunes; just sand clinging to rocky headlands as it is carried along the coast by the (delightfully piratical) longshore drift.

It turns out that everyone was right, at least some of the time.  Which is nice.  It’s hard to keep the heat in a scientific controversy when lots of the evidence, hidden beneath the surface of the sea in the first place, has been washed away or covered over during the last few millenia by terrestrial silt or aeolian sand.  Who could be angry with such mellifluous and frankly otherworldly-sounding geomorphologies in play?

Most lagoons have only been around for a little while, geologically speaking, formed after sea levels began to rise as glaciers melted 18,000 years ago or thereabouts. Many, like Narrabeen Lake, which we whizzed round on our bikes in the company of half the population of the North Beaches a few weeks ago, are even younger, not seven thousand years old. A blink of the eye for people who were here 50,000 years before.

Strangely, lagoons move.  Today’s surfers walk across the relics of yesterday’s drowned lakes.  Barrier beaches migrated landward, emerging from the ocean just as “marine transgressions” (that’s advancing oceans, not the naughtiness of waves) slowed.  Shaped in stable times, coastal lakes still don’t hang around for long.  This shouldn’t surprise me – I know that, despite appearances, beaches are really rivers of sand.
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If the tides were higher, if the rivers was faster or siltier, if Australia wasn’t so seismically serene, the lagoons would fill up and dry out or be washed away, and the cormorants would have to hunt elsewhere.  In fact, for all our dredging and draining, it’s happening right now.  Like life itself, coastal lagoons are a transitory phenomenon, a passing pleasure.
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But sometimes, under the fresh sand and brackish water there are older and odder things. The beautiful Myall Lakes, where we not long ago spent a glorious weekend, lie in the bed of an ancient river, separated from the sea not just by dunes that arrived ten minutes ago (okay, 2,000 years ago) but also by the Inner Barrier, deposited before the last glacial maximum and thirty times older.
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And then there’s the gyttja, something so very special it’s found nowhere else in Australia, and helps qualify Myall Lakes as a unique protected wetland.  What is it?  Well, rotting pondweed.  No, I’m underselling it: it’s up to 70cm of  “a highly mobile and organic mud that has a gelatinous appearance”, a “flocculent green–brown material” (Drew et al 2008), “an uncompacted, anoxic and sulphurous ‘ooze'” made from “the decomposition of charophytes, macrophytes, cyanobacteria and algae”.  Strangely, not so much about the ooze in the National Parks brochures.  But it’s an ooze that’s been there for, perhaps, a thousand years.

I’ve been thinking about lies beneath the surface of the water and the windblown sand.   But paddling through the Broadwater two weeks back, in a startling moment I found myself not gliding above the mysteries of quiet waterways, but surrounded, right amongst it.  A huge flock, a murmuration almost, of little black cormorants, perhaps returning from a fishing trip, passed above and on one side and on the other without a single cry but with a sound I’ve never heard before: the white noise of hundreds and hundreds of moving wings.

The sound of the midwinter lagoon, all around me.

* Be warned: there’s a chance my account of the origins of coastal lagoons is completely wrong.  After all, the New South Wales coast “has provoked many questions and various degrees of controversy” (Thom, 2010, 1238).  And perhaps it’s “premature to attempt a comprehensive analysis of coastal lagoon evolution and dynamics when so many lagoons have been so little studied” (Bird, 1994, 13). In case you want to check my workings:
References
  • Bird, Erik (1994) “Physically setting and geomorphology of Coastal lagoons”  in Kjerfve, B. (ed) Coastal Lagoon Processes, Elsevier
  • Davis, R. and Fitzgerald, D. (2004) Beaches and Coasts, Blackwell Science
  • Drew, Simon Iona Flett, Joanne Wilson,Henk Heijnis, C. Gregory Skilbeck (2008) “The trophic history Myall Lakes, NSW, Australia”  Hydrobiologia 608
  • Eyre, Bradley and Damien Maher “Structure and Function of warm temperate east Australian lagoons: implications for natural and anthropogenic changes” Coastal Lagoons: Critical Habitats of Environmental Change, dited by Michael J. Kennish, Hans W. Paerl
  •  Martin, Louis and Jose Maria Landim Dominguez (1994) “Geological history of coastal lagoons” Kjerfve, B. (ed) Coastal Lagoon Processes, Elsevier
  • Masselink, Gerhard and Hughes, Michael (2003) Introduction to Coastal processes and geomorphology, New York, Oxford University Press
  • Thom, Bruce, Hesp, Patrick, Bryant, Edward (1994) “Last glacial ‘coastal’ dunes in Eastern Australia and implications for landscape stability during the Last Glacial Maximum” Palaeogeography, Palaeoclimatology, Palaeoecology 111 (3-4)
  • Thom, Bruce (2010) “New South Wales” Eric Bird (ed) Encyclopaedia of the World’s Coastal Landforms, Springer

Maps in bloom

Perhaps I’ve simply been oblivious before, but this year it seems the bush around Berowra is awash with flowers –  white posies crowning the Sydney red gums (Angophora costata) that now appear to be on every street corner, ridgetop and slope.

There’s something strange about this foam of blossom appearing across our familiar view, as if, while we weren’t looking, a stagehand unrolled a new backdrop to our lives.  I’ve become a tiny bit obsessed by capturing this new scene on camera. Here’s a small sample of my multiples.  Andy Warhol eat your heart out.

Closer to town, the jacarandas are also out.  I love the way this royal bloom redrafts the map of the suburbs, rerouting your eye from the usual lines of roads and railways and wires, to a new dot-to-dot of superbly laden trees.  The city shifts on its axis.  Or better, the city’s axis, the radial city itself, retreats behind a mist of purple flowers.
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Of course, this new cartography of living things is still a map of privilege, of the breathing space between people.  They don’t call affluent parts of town “the leafy suburbs” for nothing.

Creating and keeping green space gets more urgent as cities get hotterAn article in the Harvard Gazette reports research on the way inequality, heat and green space correlate.  “Heat” says Joyce Klein Rosenthal, who teaches in Harvard’s School of Design, “is an environmental stressor, unevenly distributed in places where there are less trees, less green space, and associated with poorer housing quality”.   “At every scale” she noted “income levels are associated with surface temperatures. Poorer neighborhoods are hotter; wealthier neighborhoods are cooler”

Street trees have magic carpets beneath them, not just lilac flowers, but shade.  And on a stifling day the breath of wind across a city park – old-school evaporative airconditioning – is almost as good as the breeze off the water.  Just now, the City of Sydney is trying to green streets and villages, beating the urban heat island effect by shading concrete, weaving plants into walls and sowing seeds on roofs.

But, that hasn’t stopped the chainsaws round here.  New regulations in NSW, created in the name of fire risk-management, let householders rip, at least on trees ten metres or less from their place (oddly, it seems that trees in the middle of spectacular views present the greatest fire hazard).  What an irony: climate change, worsened by tree-felling, makes the Australian weather hotter and extends the bushfire season.  We fear the urban forests, just as we need them the most.

After years of cultivating a back yard the size of a large picnic blanket (that’s to say, a picnic blanket made of concrete) every day I bless the growing things I see from my window.  I may feel differently one day when the view from my back deck is Sydney red gums topped with flame rather than flowers.  Let’s hope I don’t find out anytime soon.