Tuesday 9 December 2014

Creature 70: Apteryx

Just a weird bird today
Apteryx is a genus of ratite birds which are commonly known as Kiwis. There are five living species in the genus. The name Kiwi pre-dates the use of the word for both the kiwi fruit and the colloquial name for New Zealanders. Unlike other all living ratite birds the kiwi is a small bird ranging from 25 cm to 45 cm in size when fully grown, depending on species. Kiwis are the only birds to have nostrils at the end of their beak. 

Like all other ratitie birds they are flightless. Given their phylogenic position and the absence of a keel bone, which is used in other birds to attach wing muscles for flight, one does begin to wonder whether the ratites could ever fly or whether they branched off from the other birds before flight had evolved. Ornithologist assure me that it has been looked into and flightlessness is indeed derived in ratites, so I will defer to their expertise.

Back to Kiwis. Kiwis are monogamous birds and they share child rearing responsibilities. Female Kiwis lay eggs that are 15-20% of their own body mass, which is an impressive effort. Male Kiwis look after most of the incubating, which I suppose is fair given the female has just layed an egg that is 20% of her body weight. Kiwis are mostly nocturnal, which is a little unusual for birds. They have quite a long life for birds with la lifespan of 25-50 years depending on the species.

All five species of Kiwi are Endemic to New Zealand and currently have patchy distributions.

Classification: The Ratites are the basal group of birds, in other words all other birds form a natural group separate from the Ratites. Their most recent common ancestor with the rest of the birds probably dates back well into the Creataceous period and the genus Apteryx probably existed as a distinct group over 65 million years ago before the K-Pg (K-T if you prefer) mass extinction. This group adds a whole new meaning to the term 'living dinosaurs' because they are, like all other birds, quite literally dinosaurs. Ratites are a gondwana relict taxon, with extinct or living species in South America, India, Madagascar, Africa, Australia and New Zealand.

Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Order: Apterygiformes
Family: Apterygidae
Genus: Apteryx

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