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Tree(s) of Life, 2008

Walpole-Nornalup National Park

Karri and tingle. Don’t they sound so southern hemisphere? OK, downright Australian? These trees dominate a little southwestern corner of the country. The red tingle in particular is tall – well tall enough to make its treetop walk a real adventure. An atavistic adventure.

Something within us must recall our early arboreal existence. How else could we be so captivated by a view down to the forest floor? Kids probably feel this more than us well-adjusted adults. Why climb trees otherwise?

Ha! Those gerygones were easy now. I could even look down at my 883rd world bird – a black-capped sittella. This is the more widespread version of varied sittella, which to us northerners is a nuthatch. Except that they could hardly be further away taxonomically. Our nuthatch sits between wrens and treecreepers, right at the New World end of the spectrum. The sittella is down with the woodswallows and shrikes in the ancient, Pangean stratum.

That’s convergent evolution in action. The super-continent’s split isolated early bird ancestors. From there many species diverged dramatically but similar environments, like forests, spawned similar looking species too. Only the genetic code can now differentiate them, give some clue to that Jurassic isolation.

It seems that the newer families of passerines grew up outside Australasia although birds’ high mobility muddies that picture considerably. Passerines are the order of birds that includes more than half the species in the world. Basically they’re the littler birds towards the end of most field guides – the birds that perch and sing and visit feeding stations. In other words, not your waterfowl, seabirds, raptors, game birds, parrots or woodpeckers.

And why are the species always in this order? As far as we can tell, it’s the sequence through time in which the higher orders and families sprang into existence. It’s a way of flattening the resulting tree of life.

With a few exceptions, like pittas, the passerines branched into vast families of South American birds before lyrebirds and scrubbirds heralded a large Australian contingent, including honeyeaters. You have to get practically all the way to shrikes, orioles and crows before European species kicked in. That’s a kind of simple, less befuddling way of looking at what is a complex, multi-level process.

Beyond the scope of this piece. I wasn’t done with the karri birds yet.

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