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

R2D2 in black and white

I’ve been spending a lot of time with magpies lately.  “Model magpies” as my nine year old aptly described these two who spent the day  posing in the Japanese maple and prancing around the back deck.  Oddly enough, the companionship steps up in intensity whenever I stop typing for a snack.

This gang of youngbloods don’t spend all their time begging for food and doing catalogue shoots, though.  There’s also the occasional training session for the Olympic synchronised vogueing competition.

And, of course, plenty of carolling.  The juveniles spent a lot of time last week singing for their supper, until one of the grown-ups got jack of the whole thing and flew down to show them how it was done.

But not before the youngsters did their party trick.  In amongst all the mellifluous warbling, my ear caught some distinct moments of robotic squeaking and clacking. The magpies were doing a bowerbird impression.

Apparently Australian birds are uncommonly good at mimicry.  Lyrebirds are famous for it, but all sorts of implausible suspects have a line in impressions as well: magpies, mistletoe birds, silver eyes. Apparently the minute brown thornbill has been recorded mimicking a pied currawong – a bird forty times its size.

Why do birds mimics the songs of others?  Pretending to be something bigger and tougher for self defense purposes seems to be one motive.  Bowerbirds have been observed doing raven impressions while being mobbed by a colony of those rather nasty bell-miners, for instance.

Another seems to be showing off to make yourself look good to potential mates.  Researchers have found that male bowerbirds that can only manage a one or two rubbish impressions (singing “like a kookaburra with bronchitis”, as the researcher cruelly remarked) have less mating success than those who can effortlessly produce a good five.

The most hilarious explanation I’ve read for bird mimicry is to chill out sexual partners.  Researchers reckon that R2D2 style squeaks and clicks that satin bowerbirds make while courting can freak out their mates:

“by interspersing melodic mimetic laughing kookaburra and Lewin’s honeyeater calls between episodes of harsh mechanical calls, males may calm females and improve the likelihood of that females will stay for additional courtship and copulation” (Borgia and Keaghy, 2015)

The idea that a sudden explosion of kookaburra calls would mellow you out and get you in the mood gives me a good picture of why certain male bowerbirds (and possibly particular male ornithologists) might be unlucky in love.

While not as famous as lyrebirds, bowerbirds do some pretty amazing impressions, not just of individual sounds but of whole acoustic scenes.  How’s this, observed from a toothed bowerbird?

A male started with the sounds of a group of people talking as they moved through the forest with their machetes cutting bushes and dogs barking, and continued with the sounds of machetes being used to fell a tree, complete with the rattle of shaking leaves after each blow and eventually the sound of the tree falling and hitting the ground with a crash (Borgia and Keaghy, 2015, 97)

The humble magpie doesn’t do badly either.  They’ve been recorded copying 21 different species of bird, as well as the sound of horses, dogs, cats and humans.  Magpies, it appears, only imitate critters that share their territory, not just the blow-ins and passers by, so it makes sense that our youngsters copy the satin bowerbirds that seem so spend much of the year in the garden, eviscerating my beans and kiwifruit vines and making free with my broken pegs.

I’ve got a whole new agenda in the backyard now.  There’s those in-flagrante males doing kookaburra impressions to listen out for.  As yet, I haven’t found any references to magpie calls appearing in the satin bowerbird repertoire.  Maybe this will be my contribution to science.  Better still, maybe I’ll catch a bowerbird in the act of ripping off a magpie doing a remix of another bowerbird.  Or the other way round.

Additional references

Borgia, G. and Keaghy, J. (2015) “Cognitively driven cooption and the evolution of sexual displays in bowerbirds”in Irschick, D., Briffa, M and Podos, J. (eds) Animal Signalling and Function: an integrative approach, Wiley Blackwell

Kaplan, Gisela (2015) Bird Minds, CSIRO Publishing