Saturday, April 4, 2009

Just how unique are the New Zealand wrens?

I have been periodically searching around for interesting Tuke stories, or experiences to add to this blog. The general fruitless of this search, if you exclude the occasional encounters of bird tickers (I'm sure there is a term for this I can't remember!) with the much photographed Tuke of Homer Tunnel, has emphasised to me how little our worlds interact. We live down in our cities, venturing out only occasionally to poke our noses into the bush. They live up there in the alpine world, sheltering in the giant clumps of rock and hopping around alpine basins in the sun, just as they have been since the Southern Alps started rising. Indeed it seems that going back in time is necessary to understand one of the reasons for why the tuke is so special.

Peter Gaze, a DOC Scientist in Nelson, plucked me an excerpt from "Consider the Birds - who they are and what they do" by Colin Tudge 2008. It begins to elucidate just how unique the tuke and its sister the titipounamu (or rifleman) are from an evolutionary perspective,

The New Zealand wrens, family Xenicidae should be treasured not simply as fine little birds but because of their unique evolutionary status. About 80 million years ago, so it seems, the world's first population of passerines split into two. One group evolved to become crows, shrikes, finches, swallows and all the rest - 6000 species of all shapes and way of life. All that remains of the other group is the New Zealand wrens."

Around 80 million years ago is about the same time that New Zealand (then a province of Antarctica) broke away from the great southern land "Gondwana". I only know this in detail because one of my current reads George Gibbs in "Ghosts of Gondwana" says so. Gibbs also notes the importance of the New Zealand wrens, here refered to as of the family Acanthisittidae...

A molecular study has revealed that our tiny acanthisittids possibly represent the closest surviving relict of the ancestral type of passerine bird

Now to be honest this doesn't really mean much to me at all, a layman in a bird mans world, but think of it this way. There are, or were, three endemic (only existing in New Zealand) vertebrate "orders", represented by the Moas, the Kiwis and the Tuatara. There are only nine endemic vertebrate families, these include our wattlebirds (eg kokako or saddleback), our family of frogs, and our special short-tailed bat of the family Mystacina. The frogs are an interesting comparison actually they have existed for a similar period of time to the wrens, have four existing species to the wrens two and three species already extinct to the wrens four.

We have 90 million years of history in our hands...