Kiwi

VulcanSpirit
Richard & Alison Brunstrom
Tue 19 Feb 2013 10:14
We've been camping in the Far North for a week, and we've seen a live kiwi - which most native New Zealanders have not!
The kiwi is the national bird of New Zealand. There are actually five species currently recognised, all very similar. They are related to the African ostriches, Australian emus and South American rheas, all having evolved on the Gondwana supercontinent before it broke up 70 million years ago. But the history of the kiwi since then is rather obscure; the oldest known fossil is only 1m years old, and most of the current species seem to have diverged from each other during the Pleistocene (2.5 million to 11 000 years ago).
It certainly is an odd looking bird:
 
North Island Brown Kiwi
 
As you can see, this is a stuffed museum specimen. It is very difficult and rather unfair to photograph kiwi in the wild as they are completely nocturnal and really hate white light from flashguns. So you have to go creeping about in likely habitat at night with a red torch. These birds are very unusual in lots of ways: they are the only birds with nostrils at the tip of their beaks, they have bone marrow like a mammal, their body temperature is closer to a mammal than a 'normal' bird, they have no breastbone (though they do retain really tiny, useless, wings). And perhaps oddest of all is their egg. Just look at this skeleton:
 
Kiwi skeleton with egg.  How does it have room for its intestines?  Or heart? And this is a brown kiwi. The little spotted kiwi's egg is proportionally even bigger for its body. (Te Papa museum, Wellington)
 
This is the largest egg relative to body size of any bird. It's hard to see how the female kiwi finds room for all her internal organs when she has this thing inside her!
 
We saw a Northern Brown Kiwi, Apteryx mantelli (species names are changing rapidly at present as DNA gives new clarity to kiwi phylogeny), in a forest reserve. It is the commonest species with about 15 000 individuals remaining (there must have been literally millions before humans arrived here). It chose to cross the path right in front of us and then stayed close-by, rooting around exactly like a hedgehog, for several minutes. Fantastic.
 
All kiwi species are threatened by habitat loss and introduced predators - they have no defence, having evolved in a world with no predators at all. At present something like 90% of kiwi chicks are killed by stoats within three weeks of leaving the nest burrow, and there is a record of a single domestic dog killing 500 kiwi in six months in the 1980s (dogs are now banned in kiwi areas).
 
Kiwi population counts are done by call. The male kiwi has a whistling shriek, repeated 15-25 times, which can carry 2km on a still night. You have to make sure that you've counted the shrieks because there are several bird mimics active at night - but luckily they get bored before they reach 15 repeats, so you can separate the true kiwis from the imposters.