Shags: here there & everywhere

Symmetrical cormorants and fake owl for crop

A pair of great cormorants not at all threatened by a plastic owl

I think I’m slowly overcoming my prejudice against ducks.  My duckism, if you like.  There’s a sudden movement on the waterline, I fumble for my camera, then I realise it’s “just a duck”.

But slowly I’ve been persuaded that ducks are worth the effort.  There’s the crazy goitre of the musk duck.   The hardhead, gruesomely named after the challenges taxidermists faced stuffing its cranium.  The nest-thieving pinkeared eared duck, with its black and white stripes and hints of neon.  The good-looking but possibly feckless chestnut teal, said to engage in “dump laying” – dropping eggs in other teals’ nests to be raised. Even shooters participating in the autumnal “kill a duck in a national park” festival aren’t allowed to blow away the increasingly rare blue winged Australasian shoveler. (Field and Game Australia chair was said to be “disappointed” about this).

In the same way, I’m slowly starting to come around to the shag .  It’s not that I’ve got a particular prejudice against them.  It’s just that they’re always there.  Whatever the time of day, season or weather conditions.  Familiarity breeds not so much contempt as slight indifference.

But these foggy winter mornings have shown cormorants in a new (filtered) light.

Cormorant raft monochrome flying bird crop square

Post-apocalyptic stillness and deep chill don’t deter them.  When there’s nothing moving – maybe just a single sea-eagle enveloped in the mist – the cormorants are the silhouettes that make that gloomy snap worthwhile.

Four of the five species of Australasian cormorants can be found on my bit of the Hawkesbury.  Only the black-faced cormorant, which only lives on the south coasts – in Tassie, Victoria, South Australia and Western Australia – has never made an appearance around here.

My favourite is the biggest, the great cormorant, Phalacrocarax carbo (or the black shag in New Zealand).  It’s the world’s most widespread cormorant, found across Europe, India, Africa and South East Asia.

The little black cormorant is lovely too, with its jade green eyes and black-on-black pattern.  I’ll never forget the feathered hush of a huge flock of them passing overhead as I paddled in  in Myall Lakes National Park a few years back.  Like other cormorants, they usually nest colonially, with lots of other waterbirds.  These little black cormorants sometimes combine in flocks of hundreds to feed cooperatively as well, a line of birds trapping fish in inlets as the tide retreats.  But I’ve never seen them flying or feeding en masse on the Hawkesbury or its tributaries.

The pied cormorant is a regular sight around here too.  I haven’t seen them nesting though, even in the mangroves of Big Bay or Spectacle Island, though flooded forests – along with coastal islands – are apparently the sites they pick to raise their young.  In the past, the pied, along with the great cormorant, were suspected by fishermen of raiding nets and at times licences were distributed to cull them.  But mostly, along with crustaceans and molluscs, they eat the small fry, too insignificant to interest human fisherfolk.

I’m not so keen on the little pied cormorants – no glamorous green eye!  I see fewer of them, though apparently they do congregate in large flocks in coastal areas.  Along with the little blacks, they’re also found right across Australia’s inland waterways and dams, feeding on crustaceans, especially freshwater yabbies, as well as little fish.

Little cormorant drying wings good wave pattern crop

Little pied cormorant drying its wings at Donnybrook Bay

I say cormorants are everywhere – from the turbid shallows at the top of Berowra Creek to the open water where the Hawkesbury meets the sea.  But that’s not strictly true.  Cormorants prefer fishing over seagrass – there’s a better range of things to eat there. And seagrass beds are under threat all over the place.  A study tracking of numbers of coastal birds at a tidal bay in Victoria for over 40 years found that not only migratory birds but the year-round residents, including cormorants, had reduced in numbers:

The marked decline in some (predominantly) fish-eating birds (Australian pelican, great cormorant, little pied cormorant, white-face heron and grey-tailed tattler) around the early 1980s closely matches the beginning of a decline in commercial fish catch… Decreases in fish-eating birds and fish coincide with substantial losses of seagrass in the bay (Hansen et al 2015 524)

Cormorant about to be eaten bigger square

Cormorant avoiding a shark at Dusty Hole in Berowra Creek

And it seems, cormorants tend to steer clear of shallow water, no matter how good the spread, if there’s sharks about.  Just another reason for a kayaker to love a shag!

Egg blue sky and fog on beach at Twin Beaches

Egg the ancient kayak at Twin Beaches

Additional references:

Dorfman, E.J. and Kingsman, M.J. “Environmental determinants of distribution and foraging behaviour of cormorants (Phalacrocorax spp.) in temperate estuarine habitats” Marine Biology 2001 138 1-10

Hansen, B., Menkhorst, P., Moloney, P and Loyn, R. “Long-term declines in multiple waterbird species in a tidal embayment, south-east Australia” Austral Ecology (2015) 40, 515–527

Heithaus, M.R. “Habitat use and group size of pied cormorants (Phalacrocorax varius) in a seagrass ecosystem: possible effects of food abundance and predation risk” Marine Biology (2005) 147: 27–35

Traylerd, K.M., Brothers, D.J., Woollera, R.D., and Potter, I.C. 1989 “Opportunistic foraging by three species of cormorants in an Australian estuary” Journal of Zoology (1989) 218, 87-98

Cormorants in mist

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