Huias, Takahes and the price of sexual dimorphism

In amongst the detritus that was my last post, I made a brief list of those birds that I could remember as having become extinct in the recent past; the dodo, the passenger pigeon, the moa, the elephant bird, the great auk, those birds that humanity, if it had a collective species memory, might remember and perhaps rue its rôle in the annihilation of a unique compenent of the biosphere. In doing so, I made a glaring omission. Not because I had forgotten it, it is a bird in which I am quite interested for the most tenuous of reasons, but mainly because few outside New Zealand or the field of ornithology would be aware of its name, much less its one-time existence. Moreover, it was not hunted to extinction for food but for another quite dubious and almost reprehensible reason.

The bird in question is the Huia and a primary reason for its demise, in the early part of the twentieth century, was the practice of taxidermy! Every museum of natural history wanted a stuffed and mounted pair (and it had to be a pair, one female, one male); as a taxidermist one could become rich stuffing Huias, the market was huge in the late nineteenth century. What intrigued museum curators in the western world was an example of extreme sexual dimorphism not seen in any species of bird yet encountered.

Sexual dimorphism is simply a 'posh, scientific' phrase to denote differences between the sexes of a species; it is very common in the animal kingdom and often relates to a female's choice of certain characteristics which she 'finds desirable' in a male; Darwin's 'Sexual Selection'. The males of Guinea Fowl are more ornate than the females, more brightly coloured or, as the in the peacock, excessively flamboyant. The male Bird of Paradise, whatever the species, are as rococo as a Regency Dandy in their bid to attract a mate. Male great apes, including us, are larger, more physically robust in the main, than the female, although conversely it is the female raptor, bird of prey, which is significantly larger than the male. However, despite obvious differences among the sexes of many species, the Huia was almost unique in the need for pairs, not just one. Why should this be so, I hear you ask?

The birds were almost identical in size whatever the gender, they were uniformly black, but with a green iridescence when the light caught the feathers, much like a magpie, and both sexes possessed two red  'wattles' on their cheeks behind the bill and it was the bill (beak) which made the Huia almost unique; the male and the female had different sized and shaped beaks! This is perhaps best illustrated by a watercolour sketch from the famed British, Victorian artist and lithographer, John Gould. The female is the uppermost of the two:

Quite why the Huia should possess different beaks for the two sexes is a matter for conjecture. It is possible that they used different food sources for part or all of the year; the female would be able to burrow deeper in the rotting tree bark for grubs, which were their primary food item, than the male and this may have provided an advantage especially with young too feed in addition to themselves. Peregrine falcons, for example, do much the same thing. The female, being 33% larger than the male, can tackle commensurately larger prey and so one species of prey is not put under undue predation pressure from both birds in a pair.

While some of the blame for the Huia's decline can be laid at the door of the Māoris, who hunted them for the tail feathers* to decorate themselves with, it is unlikely that the Māoris posed any real threat to the survival of the species as a whole, although it is quite possible that their numbers were substantially reduced as a result of this practice and, by the time of European settlement, any recovery from the depredations of the Europeans was no longer possible.

The 'Victorians' in Europe and the USA had an entirely different perspective on the natural world than is prevalent today. They generally believed in the spirit, if not the letter, of the adage that mankind had certain rights '(to) let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth', dominion over all the beasts of the world; the wildlife of the 'third world', such as it was, was inferior to the wildlife in Europe or the USA and of little import; wildlife 'artists' would invariably work from skins, rather than life, and often shot the birds for the skins themselves!

As a consequence, the survival of a bird or an animal in the wild, alive in its natural habitat, was in general of no concern to the Victorian naturalist providing that a suitable 'stuffed variety' was held in the local museum or national collection. Huias were killed in the thousands for specimens, which coupled with the extensive deforestation of the Huia's natural habitat in the south of the North Island in order to provide agricultural land for the incoming settlers proved devastating. By 1920, they had gone forever**.

The birds of New Zealand contain some of the rarest species of bird on the planet. For much of its recent past(in geological terms) it has been an island (two islands) with no ground living mammals or marsupials until the arrival of man some 1500 years ago;, the birds evolved in an environment of largely danger-free tranquillity and in many cases evolved into niches which are occupied by mammals elsewhere on the globe; as a result they have had to deal with not only hunting and deforestation but also direct competition for which evolution has not equipped them.

We have already lost nine species of Moa. those giant ratities, to the Māoris, three hundred years before the Europeans arrived, as well as the Huia. One can only hope that despite a general population crash of indigenous ground dwelling birds, the takahe, the tui, the kiwi, the kea***, the kakapo, occasioned by the introduction of mammals by Europeans in the nineteenth century, that the measures now in place will continue to protect and nurture what remains of this unique fauna.,

* A Huia tail feather attracted the largest bid ever for a single bird feather at a recent 2010 auction, NZ$8,000 (£2,100, $3,200 or €2,5000); the things people will spend money on!
** A few sporadic sightings were made in the 1920s and the 1950s but no-one gave, or gives them much credence.
*** The kea, a type of parrot, has an insatiable curiosity and little fear of humans. An ex-boss of mine, a New Zealander, once had her 15 minutes of fame as a child from a local news report. Her friends and she were wont to roll down a hill for fun; it was not long before a local kea joined them in the activity every day. When the children stopped for the day, the kea would just amble back into the wood!