Wildlife reboot: birds 2.0

Another January, and another trip to Ganguddy, on the western site of Wollemi National Park.  Same marvellous geology, same refreshing dam water, same hot weather.

But some things were different this year.  After the stupendously dry winter, the eucalypt forest was parched, the undergrowth sparse and the leptospermum flowers of last year’s visit few and far between.  We found a patch of sphagnum moss perched in a bowl of sandstone boulders so dry it crunched underfoot.

A “green” satin bowerbird panting in the heat

We spotted plenty of lizards, and the diggers were out in force – lyrebirds wandering through the camp as they tried to scratching their way down to moisture and a wombat turning up to twerk on a picnic bench.  But up in “kingfisher alley”, just before the Cudgegong River disappears into the reed beds, there were fewer blue and green flashes by the water.

Around the camp site, the bowerbirds and treecreepers panted in the heat.  Apart from the ubiquitous reed warblers, there seemed fewer birds altogether.  No sign of the friarbird teenagers of last year, and even the baby swamp hens seemed thin on the ground.

You have to wonder what it takes to change ecosystems irrevocably.  How many dry winters before the old inhabitants decide living and breeding here is just too tricky?  And who would move in to fill their place?

Back at Berowra after the trip, there are changes in the garden too… surprising ones.

We knew we’d be losing the sparrowhawks soon enough, but the family has dispersed in an unexpected orderThe adults disappeared off the scene weeks ago, and by the time we made it home with our ridiculously overloaded vehicle and small and ancient fleet of boats, the siblings had parted too.  There’s just one young’un now.  He seems lonely.

There’s a constant plaintive calling from the trees out back, that seems to intensify when he has prey on hand.  I’m not quite sure if he’s warning his imaginary sibling off or calling him to come and share a meal.

And that’s not the only shift in the soundscape around here.  The sparrowhawks have cut a swathe through the bird population on the premises.  Baby brushturkey numbers have fallen from previous plague proportions, noisy miners are few and far between and the “house” birds of yesteryear – red and little wattlebirds – are now just occasional visitors.

But as the numbers of resident raptors has dropped, a new set of critters have settled in.  Lewin’s honeyeaters which we’ve only seen once or twice in the backyard over the last seven years, have made our backyard their new home.  And we also appear to have acquired some brown thornbills, a raptor snack food if ever there was one.  And the local eastern spinebills, another tasty morsel for a sparrowhawk, are spending more time around here too.

The only explanation I have for the change of personnel is that the hawks have bumped the notoriously territorial wattlebirds, leaving the field open for new arrivals.

I’m pretty happy to have a new set of birds in the garden.  My dream scenario, I have to admit, would be to order up some songbirds that are a bit easier on the eye.  My birdwatching brother puts Lewin’s in a honeyeater “bin taxon” of pretty similar and drab looking birds it’s hardly worth distinguishing between.  Cruel, perhaps, but fairly accurate.

So, why not some new holland honeyeaters, for instance – gorgeous looking locals.  Or (still, my beating heart!) what about some pardelotes?  Just one or two?

On the other hand, it’s possible that all the vibrantly coloured small birds in the neighbourhood have been made into multicoloured meals over the past three months by our family of raptors.  After all, there’s got to be some evolutionary reason for all those SBBs*.

*note: this is a throwaway remark absolutely unsupported by any science.

 

Previous posts about Ganguddy

A bit about Ganguddy’s history and geology – and a little Tim Low on the side

Snakes versus whining teenagers – last year at Ganguddy

 

More on our sparrowhawk summer

Death and sibling rivalry

The new generation of sparrowhawks emerges from the nest…

Baby brush turkeys versus nestling sparrowhawks… the battle of the backyard baby birds

The collared sparrowhawks return to our backyard… or are they brown goshawks?

A first glimpse of the sparrowhawks… and a beautiful white goshawk visits the washing line

 

Further reading

Stephen Garnett, Donald Franklin, Glenn Ehmke, Jeremy VanDerWal, Lauren Hodgson, Chris Pavey, April Reside, Justin Welbergen, Stuart Butchart, Genevieve Perkins and Stephen Williams (2013) Climate change adaptation strategies for Australian birds: Final Report, National Climate Change Adaptation Research Facility

Office of Environment and Heritage, Premier’s Department (2011) New South Wales Climate Impact Profile Technical Report: Potential impacts of climate change on biodiversity

Death & sibling rivalry

Both birds eyes crop better again

The sibling sparrowhawks in their favourite tree… in my backyard!

It’s happened. Our babies, only three weeks or so out of the nest, are now out there in the big wide world, killing for themselves.  It brings a tear to your eye.

Distant with second bird flying crop

Keeping an eye on little brother or sister

But it’s not all cheery dismemberment:  there’s trouble in the nest.  The siblings to have an uneasy relationship.  I often see them perched on adjacent branches, and when they’re further apart they call out to each other every now and then.  And when one takes off to hunt, the other often falls into line, disappearing suddenly in a simultaneous dive.

But there’s also a certain amount of what might be described in human siblings as petty jealousy.

Yesterday I stood on a chair on the deck for an hour watching one of the sibs engage in  a comprehensive preening session / extended tai chi practice.  I wonder whether this serious self-care might have been the consequence of getting tangled up in one of the humungous org spiders webs stretched out between the trees to catch dragonflies, cicadas and, for the really ambitious arachnid, a passing sparrowhawk.

Preening headless profile tail out crop b&w

… and the headless sparrowhawk

I found the “revenge of the headless raptor” impressive, but his nestmate, looking on from a high branch, seemed rather unimpressed.

Distant top brother looking down b&w

Jeering at silly sibling

But both martial arts and sneering were set aside when the fledgling in the upper branches spotted something tasty beyond the neighbour’s yard.

Juvenile sparrowhawk wings raised square

I’m off…

There was a simultaneous stoop, and then a fracas in the jungle at the bottom of the garden.

White cheeked honeyeater crop

Dinner… a white cheeked honeyeater I prepared earlier

I don’t think the squawking was the work of dinner – an unfortunate white-cheeked honeyeater (rarely seen in our yard.  I wonder why…).  I reckon the ring-ding battle was between the sibs.

The winner landed, very conveniently for me, right next to my washing line, showing the total indifference to human proximity that seems to characterize most young raptors.

 

Sparrowhawk profile left with untouched prey

The lucky sibling with significantly less lucky white cheeked honeyeater

This diffidence did not extend to the presence of little brother or sister though.

Juvenile looking behind for rival

Keeping an eye out

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Juvenile with head turned mouth open amended

 

Just a few moments after the winner landed with their prize, there was another skirmish.  Luck favours the prepared, and this youngster was in position, with wings spread out protectively around the prey like a sort of meat umbrella. Ew, what a nasty image.

The hungry one had another go, and to be honest, I’m not really sure who was successful, since neither juvenile has any distinctive marks (like a scar over one eye or a dragon tattoo or anything) I am completely unable to tell them apart.

Juvenile plucking the prey

Settling in for a good plucking

Anyway, someone had a lovely meal of raw songbird and someone sat nearby looking on and feeling sorry for themselves.

Sibling watching

Luckless sibling looking on at the feast

Nevermind, buddy.  I’m sure there’s be some tiny, tasty, rather slow birds on the menu for you sometime soon.

The backstory of the serial killers in our backyard…

The new generation of sparrowhawks emerges from the nest…

Baby brush turkeys versus nestling sparrowhawks… the battle of the backyard baby birds

The collared sparrowhawks return to our backyard… or are they brown goshawks?

A first glimpse of the sparrowhawks… and a beautiful white goshawk visits the washing line

Welcome back, beautiful stranger

Sparrowhawk square crop old

It shows a certain lack of character and imagination to be keen on raptors, but I can’t help it.  I love them anyway.  Even the whistling kites and white-bellied sea eagles I clock every single weekend out in my boat on the Hawkesbury give me enough of a thrill to  clog up my computer’s hard drive with a thousand pictures of them in every conceivable posture and mood.

So two years ago, when I caught this beauty in my backyard, I was beside myself with excitement.  It’s a collared sparrowhawk, one of three species of Acciper found in Australia, along with the very similar brown goshawk and the hauntingly beautiful grey goshawk.  So beautiful that on my one and only encounter with one (whilst pegging out the washing) my camera fainted and so in its barely conscious state was only capable of producing a groggy quasi-mystical image of the world’s only pure white raptor.

I know our beautiful visitor in 2015 was a sparrowhawk and not the very similar looking brown goshawk, having been schooled on the key differences.  Brown goshawks are slightly grumpier and more threatening looking, with a beetle brow and chunkier legs.  Both species, it is said, waggle their tail on landing, but the sparrowhawk does it a tiny bit more rapidly.  As my brother, a much more expert bird watcher than I am, points out, this has to be the most arcane and pointless advice for distinguishing two very similar looking birds.  “Sorry lads, the video of your tail waggling was slightly out of focus.  Can you just circle round and land side by side on that branch again?”

Collared sparrowhawks also have another feature – the absurdly long middle toe of the collared sparrowhawk, used to grip its prey while it systematically plucks them (starting at the vent) and then devours them.  It’s moments like these you’re grateful not to be a sparrow or a silvereye, isn’t it?

But is that enough to tell the difference between a goshawk and a sparrowhawk?  Both apparently have these long middle toes – the sparrowhawks’ toes are just longer and more delicate.

There are other differences too.  Goshawks have a rounded tail, and a smaller eye.  So is it welcome back stranger… or good to see you, lifer?

Both the collared sparrowhawk and the brown goshawk are widespread through their range in Australia and New Guinea – they can be found in arid areas as well as woodlands and suburbia.  They are one of the few raptors that will perch and hunt in gardens, as I saw today.  The fact that they’re partial to a snack on introduced birds like sparrows, starlings and newly hatched chickens (gulp!) may be one reason why they’re considered “of least concern” to people who worry about the current mass extinction event.

But still, they’re not exactly common. Numbers declined from the 1940s through to the 1980s thanks to DDT, although the effect of this insecticide – thinning the shells of eggs – seems to have been less dramatic for them than peregrines and some other raptors.  Loss of habitat for the small birds that sparrowhawks like to eat and competition from pied currawongs that will (somewhat implausibly to my mind) attack both adults and chicks are other threats.

It’s been a long couple of years since that last wonderful visit.

But over the last few days there’s been a new sound from the decrepit pine trees that stand (or should I say lean) between our place and our neighbours’.  At first I thought it was a whiny juvenile wattlebird begging for a feed – the call was a kind of feeble high pitched kik-kik-kik-kik.  And then I saw a creamy coloured bird with wide striped wings and a blunt head, superficially like the “green” satin bowerbirds that hang around here all year round scrounging off my chilli bushes and demolishing my bean plants.

But there’s something distinct and decisive about the way raptors fly.  I eventually got a good look as the bird chilled out in the trees, waiting to ambush passing little passerines, which they catch on the wing.  I’m really hoping they have a taste for noisy miners.

good sideways distant crop wide

These really are very low-key birds.  “Often lives unnoticed in mature-treed suburban parks and gardens” one ornithology site comments about sparrowhawks… “easily overlooked”.  Having spent quite a bit of today staring slightly hopelessly into the naked branches for an immobile, unconcerned and well camoflaged bird of prey I can confirm this.   “Trusting and approachable“, the Peregrine Trust’s turn of phrase for a collared sparrowhawk, seems like a slightly embarrassing description for a predator.

Sparrowhawk profile crop tighter still

A gorgeous profile on display.  One very chilled out bird.

The grumpy reputation of Brown Goshawk is apparently not just a consequence of their Resting Bitch Face.  They’re also apparently quite aggro around the nest.  True to form, sparrowhawks are said to be calmer.

Perhaps this parental behaviour will be the solution to my ID problem.  There’s a nest made of sticks high in the neighbour’s pine tree, a spot I saw the sparrowhawk returning to several times today.  If there’s anything better than grown up raptors in your backyard, it’s a clutch of baby raptors.

nest rop

Could this be a sparrowhawk nest?

A confluence of critters

dawn-small

Another sunrise, another paddle through a flooded river valley.  At Port Stephens the wide Karuah River meets the Myall as it meanders south, just behind the coastal dunes.

And where the water flowing from the network of wetlands and lagoons that is Myall Lakes joins the estuary, in a river delta protected from the destructive power of the Pacific waves, there’s Corrie Island.

A spot so fabulous for cautious amateur photographers in small and ancient boats, I circumnavigated it at the crack of dawn not once but twice over the silly season.  I may have been so exhausted I wept all over my Christmas crackers but it was worth it.

Just down the river from the RAMSAR protected wetlands at Myall Lakes, migratory birds that breed in the far north spend the arctic winters hanging out here.  I saw red knots (heads up: not very red in the non-breeding season) and grey tailed tattlers, far eastern curlews and bar tailed godwits.  In fact, I was treated to a bold dispay of the very barred tail of the bar tailed godwit, that tail that make the longest uninterrupted migration flight of any bird’s behind.

The eastern ospreys, in my previous experience elusive canopy lurkers, proved so indifferent to human proximity that I actually got bored with taking photos of them posing in the beautiful dawn light, and starting trying to snap the LBBs in the beachside brush, while the ospreys observed my inadequate efforts with golden eyes.

osprey-3-d-claws-crop

osprey-looking-at-me-crop-square

two-ospreys-2-square

A pair of eastern osprey?  The females are larger.

And just when you thought it couldn’t get any better, here come the dolphins.

The famous pod of Port Stephens dolphins – well, the easterly, sociable estuarine pod, one of two quite distinct groups that lives in the harbour – swung by to check me out.  I stopped still in the swell, watching them case the beach. At one point the still water by the boat upwelled and the tip of a bottle nose appeared above the surface for just a second or two a couple of metres off the bow.

island-with-dolphin-longer-fatter

Enter a caption

A couple of mornings later, I was back, having rashly promised my birdwatching brother dolphins, ospreys and eagles.  No need for a refund: they arrived one after another, right on cue.

And in between boat trips, it wasn’t just overeating and board games either.  There was also watching the local bird life overeating.

A baby sitella not quite sure how to handle the festive gift of a caterpillar…

And an Australian hobby enjoying Christmas dinner with us, swooping in to a branch above our holiday rental for some yuletide disembowelling.

I think we’ll be back.

egg-on-the-beach-at-end-of-da

What’s inside the bird cage?

Not artichokes.

I spent all of last autumn dreaming of artichokes.

In the three years since my last bumper crop, which grew splendidly with no attention at all while we were half a world away, I have tried and failed to get more magnificent edible thistles towering over my veggie patch.

Our garden is a challenging environment for any seedling.  I suspect the sad fate of the last two generations of artichokes can be attributed to the deep gloom that descends on the yard around the time of the autumn equinox.  But there are other possible suspects in the frame…

Yes, rabbits.  My transition to the Mr McGregor, the homicidal carrot fancier in Peter Rabbit is now complete.  But so far I’ve avoided GBH with a shovel.  Instead I got me a fine flock of bird cages.

A budgie lover in Berowra must have had a mass break-out just before the last heavy rubbish day and I was the lucky beneficiary.

But my visions of bounty weren’t to be.  I’m not sure if some small but dextrous herbivore lifted up the tiny food hatch and sneaked in for a unappetising meal of baby thistles or if the artichokes lost the will to live in dank captivity.  On the upside, budgie cages are evidently great at keeping rabbits off your rocket.

Not strawberries

So, there are no artichokes in my bird cages.  And so far, there’s no strawberries either.

My other score from the last council cleanup was a load of aviary wire and some nice hardwood architraves.  A few bucks on hinges and I was able to put into place the final stage of my termite-assisted plan to reduce my erstwhile (and totally pointless) garden path into rotten timber. My aim: to grow strawberries under the flight path of the gate-that-used-to-be-a-bed.  Or more precisely, to grow strawberries for human rather than chicken consumption.

I was pretty happy the outcome of my chookhouse-tolerances joints, held together with an assortment of mixed screws from the jar at the back of the cupboard.

Thus far the chooks haven’t managed to break in but the strawberries seem somewhat oppressed by their location.  Every day is a bad hair day.  I’m hoping they’ll be ugly but productive but the signs don’t look good so far.

On the bright side, lazily throwing scratch mix over the gate has produce a little protected patch of green in the razed earth of the chook yard.  I’m not sure the strawberries enjoy the competition from wheatgrass, but the hens have a hippie feast every time I do the weeding.

Fewer chickens than there oughta be.

Sadly, on one bleak and rain drenched evening in the middle of winter, most of our hens weren’t in the birdcage either.  Only Cyan, bottom of the pecking order thanks to her gammy eye, and Treasure, broody as usual, were in Colditz, the predator proof cage, when a hungry fox came to visit.

Only one of the chooks that had been perched in the favoured roost, the potted fig tree, survived, a fairly run-of-the-mill Barnevelder whose name we could never quite remember.  After the slaughter, we renamed her Xena as a mark of her prowess in battle.  Bold and beautiful Cleo, curmudgeonly Snowball, at least 8 years old, feisty Morgan, shy but reliable Abby and inexpertly named Tigress all disappeared or were found in bits in the yard the next morning by the shellshocked RB.    Given the sad end of Shyla under similar circumstances at the same season the year before, you can only conclude we are poor chicken keepers and, frankly, very slow learners.

So now, come rain or shine, you’ll find our remaining hens locked up every night.  At the moment, it’s a lonely night for Xena, locked up in Palm Beach.  Her mum, Treasure, laid low by has some mysterious ailment, has been in the intensive care ward in the laundry, while one-reviled Cyan has now attained the pre-eminent position of queen of Colditz, adoptive mother to three new day-old chicks.

Fortunately, Xena can always rely on her playdates.  Just like next doors’ kids, the neighbours’ hens nip through gap in the fence and hang around outside waiting for our girls to be let out for the day.  They share a feed and if we’re lucky lay an egg or two on our side of the “magic portal” (to clarify: we get eggs from the chooks but sadly not the kids).

Three cheers for the return of stay-at-home scrumping!  Low-level food thievery without even leaving your own backyard.

And no baby brushturkeys

Until they’re 12 weeks old, the chicks are confined to Colditz along with their adoptive mum, in case they get eaten by a kookaburra or pecked to death by one of their loving aunties.  None of them are taking imprisonment well.

Smuggling the chicks (sexed and vaccinated and genetically disparate) under relentlessly broody Cyan at the crack of dawn was a doddle. Especially compared the sleepless night I spent as a ignorant featherless human trying to keep the wee things safe and warm in a cardboard box under a desk lamp without setting the house on fire.

chicks-in-sunlight-eye-open-crop

They were happy at first.  But these days, the chicks and their mum spend most of their time pacing the length of the cage, apparently hoping to find a hidden exit.  Their only distraction is the thrill of scratching through the bug, straw and leaf litter mixture left in the potato patch after this year’s laughably miniscule harvest of spuds.

They’re particularly plaintive when they have visitors.

I’m not sure if all that frantic peeping is concern that one of their number has apparently gone astray from the flock, or jealousy that the baby brush turkey is free to roam the yard at will.

The little brush turkey spends a surprising amount of time close by, staring intently into the cage.  Perhaps there’s something more to it than the chick crumble dropping through the wire floor.  One night, tiptoeing down to shut in Xena for the night, I saw him roosting there, right on top of the cage.  Strange behaviour from a chick that never meets its siblings or its mother, let alone snuggling together with them at night.

Blood feud in the dawn redwood

male-koel-neck-arched-square

Every year for the last seven years, I’ve heard koels calling, loudly and desperately, right outside my window, day and night, for the three months from the equinox to Christmas.  And for the whole of that time I’ve been trying to get a decent photograph.  A while back, I caught sight of a whopping great juvenile sitting around on a branch of the pine tree, whining for more food from his adoptive mum, a harassed looking red wattlebird. But that’s it.

I know they’re there, skulking in the trees, the males advertising their availability in an increasingly high pitched, eventually hysterical squeak from the cover of the leaves.  And there’s that duet that koel couples, both equally well concealed and well amplified, produce – the male exclaiming “wurru-wurru!” while the female interrupts with a simultaneous “keek keek keek!”.  But where are these potentially ear damaging exchanges coming from?  Who can say.  It’s like trying to locate a pair of shy and slightly drunk ventriloquists.

But that all changed in my backyard yesterday.  I’ve finally got my stash of koel shots.

Why did these cryptic birds let me get close enough to take a million pictures?  I reckon it was because there was a battle on in the branches.   The prospect of scoring, through combat, a romantic enounter with the iridescent, satan-eyed male seem to make the feuding females oblivious to all that clicking and crashing in the undergrowth.

The  sexual proclivities of koels are not well understood (by humans anyway.  You hope koels have a decent grip on it).  Brood parasites are inherently interesting critters, so koels’ interactions with the honeyeater “hosts”, whose nests they visit to lay their eggs, has been studied exhaustively. The changes in their migrating habits as the world warms up have been looked into a bit as well (eg Chambers et al 2014).  But how and with whom they do their coupling is all a bit of a mystery.

You can’t give the ornithologists too much grief about this.  Even the most avid twitcher is going to be a bit dubious about spending the three years of a PhD shinning up trees clinging to a GPS tracking device, in an attempt to pin down the sexual encounters of an intercontinental migrant of no fixed abode.  And that’s not even considering the koel’s antisocial habits: the fact that they are “typically wary and difficult to observe [remaining] in thick foliage, high in trees, calling from concealed positions” (Healy and Healey 2007).

female-koel-peeking-around-leaves-crop

So what did I see (or half see) in our metasequoia tree after breakfast yesterday?

Did I witness a female, already partnered however temporarily with Mr Shiny Feathers, being challenged by a youngblood for access to a mate?  Koel males are apparently “polygynous” – they mate with multiple females.  But those ventriloquist duets suggest some kind of short-term liaisons, since couples that sing together like this, apparently, often have some kind of ongoing arrangement (Maller and Jones, 2001).

Or just two females both keen to hook up with guy who had command of such a fine calling station, my beautiful dawn redwood?

 

The male was staying well out of it, watching cagily from the side lines.  At one point I spotted him passing somethinga nuptial gift of a berry? – to one of the warring females.  I didn’t see if him get anything in return, unlike the lucky Asian koel spotted by this Singapore based bird watcher. But then with bird couplings, blink and you could easily miss it.

koel-eating-a-seed-crop-for-amend

Female koel… with nuptial gift?

 

But if the male bird was playing favours, this was strictly a chick fight.

At first it was a rap battle.

Eventually the two females settled at opposites ends of a branch, studiously ignoring each other, like gunfighters in a Western pacing the far ends of Main Street.  And then it was on, with a flurry of feathers and a fanning of tails.

two-koel-on-branch-flipped-and-cropped

Two female koels about to tussle

 

Such chick fights aren’t as unusual as old-fashioned zoologists might think. Females that live in groups, it seems, often engage in “intense female-female competition over reproduction, dominance rank and other components of social-living” (Rubenstein, 2012, 2250). I’ve seen it with the chickens.  According to the implausibly named Clutton-Brock and Huchard, in a recent article for the Royal Society these fights “peak… during the reproductive season [8183], and … can lead to wounding or death [28,84].”  And fights are not just about access to mates, but about protecting eggs or nesting sites, space or foraging territories (Tobias et al, 2012; Krieg 2016).

Intriguingly, competition between females seems to go along with good looks or “ornamentation”.  Or better still “ornamentation and weaponry”.  And female koels, while not obviously armed to the teeth, surely are beautiful birds; like most ornamental or colourful females both substantial in size and hailing from the tropics (Dale et al 2015).

sideish-female-koel-with-good-view-of-stain-include-square

Hang on, what is that mysterious red stain on that creamy chest?  Was this a battle involving “wounding or even death”?  Was I witnessing an injured female being challenged, in her moment of weakness, by a healthier rival?

In some of my photos it surely looks like it.

Is that a blood stained beak?  Was this a ghoulish outcome of a predator attack followed by a desperate battle for genetic survival?

female-koel-with-red-beak-squareOr is it just mulberry season?

References

Chambers, L E, Beaumont LJ, Hudson IL (2014) “Continental scale analysis of bird migration timing: influences of climate and life history traits” International Journal of Biometeorology 58 (6) 1147-62

Dale, J., Dey, C, Delhey, K, Kempenaers, B, Valcu, M. (2015) “The effects of life history and sexual selection on male and female plumage coloration” Nature Vol 527 pp.367-71

Healy, C and Healey, E (2007) “Diet and Roost-site Fidelity in the Common Koel
Eudynamys scolopacea in Suburban Darwin” Australian Field Ornithology 2007, 24, 184–186

Maller, C J and Jones, D N (2001)”Vocal behaviour of the Common Koel, Eudynamys scolopacea, and implications for mating systems” Emu, 2001, 101, 105–112

Rubenstein, D.R. (2012) “Sexual and social competition: broadening perspectives by defining female roles”  Philosophical Transactions: Biological Sciences, Vol 367 No 1600, 2274-2293

Tobias, J. et al (2012) “The evolution of female ornaments and weaponry: social selection, sexual selection and ecological competition” Philosophical Transactions: Biological Sciences, Vol 367 No 1600, 2274-2293

Krieg, CA, Getty, T. (2016) “Not just for males: females use song against male and female rivls in a temperate zone songbird” Animal Behaviour Vol 113 39-47

 

Fly in, fly out

The first asparagus is up.  The greenflies are sucking the life out of the few broad beans plants that survived the gnashers of the garden’s winter visitors.  The bowerbirds are brutalising the new growth on the liquidambar, in a jaunty colourised style that makes me think we have a flock of Calamity Janes in the canopy.  Spring is here!

But what about the spring birds?  I haven’t heard the first koel of the season, but the channel billed cuckoos have squawked their way into our dreams.  And in the last week, a new rolling trill in the trees: the olive backed orioles have returned.  We rarely see them around here, but according to Michael Moorcroft’s “Birds of Australia” as “common”.  The emergent twitcher in me sighs.

I met a charming French skin specialist once, and asked her why she moved to Sydney.  “We have melanoma in France of course” she said “But really, if you are interested in skin cancer, Australia is the place to be”.

On the other hand, if you long for the sight of that first feathered visitor arriving from a epic transcontinental journey, you’re better off in the Northern hemisphere.  All the ocean in the southern half of the globe, moderating seasonal temperatures; barriers of forest and ocean; a less icy past; uncertain rainfall and an often arid climate; and (somewhat unconvincingly) weirdly, lots of  “V” shaped continents; all reasons I’ve come across to explain why we have so few migrating birds around here (Someille et al 2013; Dingle 2008).

Back home, two thirds of my French oncologist’s local birdlife would be part time residents.  But in Sydney, it’s maybe one in five.  In the outback there are nomads, roaming around trying to find things to eat in an arid landscape, but there are hardly any regular migrants at all.

silver-eye-chestnut-4-crop-larger

Tasmanian silvereye mid-migration, Zosterops lateralis lateralis

What we do have lots of in Australia are “partial migrants”.  Somewhere between a third and a half of bird species have some sedentary individuals while others take off in the colder weather (Chan, 2001).  Most silvereyes, for instance, stay put, but many Tassie birds – chunky numbers with chestnut sides, like the one above – fly across the Bass Strait in winter, possibly island-hopping as they make their way to Victoria, NSW and Queensland.  On my way to work the other day, I was was befuddled by the strange appearance of a crew of migrants – on their way home, perhaps – milling around happily in the company a bunch of plain-brand silvereyes.

Hard working bird lovers have been tagging silvereyes for 30 years (Chan, 2001), so we know what these guys are up to.  But in general, partial migrants are tricky customers – figuring which of the identical birds you see are interstate visitor and which are locals is mostly pretty hard to do.

After reading a bit about research on bird internal navigation systems, I’m starting to think this kind of deviousness may be payback.

One set of experiments involved keeping captive birds and observing what corner of their cage they batter themselves against, driven by migration-restlessness or Zugunruhe (one of those cool German words for which there is no English equivalent).  Researchers messed with the heads of these captive birds, using mirrors to shift the apparent direction of the sun so they could see what new quadrant of their cage they try to escape through.  Other experiments placed caged birds inside a magnetic coil to warp their sense of direction – a research activity truly worth of evil genius from X-Men. Although I do find the thought of a bunch of 1940s songbirds flooding into a planetarium – another early experiment – quite charming (Burton 1992).

 

dawn-moon-best-tight-crop

If you do see a trans-continental migrant in Australia, it will probably be a shorebird.  About 35 beach loving species migrate here (Dingle, 2008).  On a paddle up Mooney Mooney Creek last weekend, I was really happy to see one of them: an eastern curlew, its absurdly long beak mucky after joyously feasting on the mud-flat crabs off Spectacle Island.  Flying from Siberia will take it out of you. Between the bloody photographers, the houseboats and the jet skiiers, it’s not hard to see why these guys are classed as critically endangered around here.

 

 

References

Burton, Robert (1992) Bird Migration, London: Aurum Press

Chan, Ken (2001) “Partial migration in Australian landbirds: a review” Emu, 2001, 101, 281–292

Dingle, Hugh (2008) “Bird migration in the southern hemisphere:
a review comparing continents” Emu  (108), 341-59

Somveille M, Manica A, Butchart SHM, Rodrigues ASL (2013) Mapping Global Diversity Patterns for Migratory Birds. PLoS ONE 8(8): e70907. doi:10.1371/
journal.pone.0070907