Raymond Dixon, of Waikanae, asks :-
Why doesn't New Zealand have colourful birds, as exist in almost any other country.
Kevin Burns, a zoologist at Victoria University of Wellington, responded.
Fantastic question Raymond, it really got me thinking.
Most of the colourful birds you have in mind are tropical, are they not? Birds-of-paradise, toucans and bee-eaters are very colourful and largely restricted to tropical latitudes.
An over-representation of colourful types of birds in the tropics may be the result of a simple numbers game. The tropics have more bird species. If bird groups are distributed randomly across the planet, then areas with higher bird diversity should passively ‘sample’ more colourful birds than less diverse areas. This is the simplest explanation that I can think of for the absence of really colourful birds in New Zealand.
However, there is good reason to expect our avifauna to be less colourful than most. Bird predators reigned supreme in New Zealand before we arrived. Most predatory birds are visual hunters. So we might expect many of our other bird species to have evolved drab plumage to blend-in with the bush and avoid being eaten. Kakapo are perhaps the best example of this. They freeze when threatened and turn their greenish-brown backs to the world in the hope they won’t be spotted.
But despite the need to hide from visually-orientated predators, I think that New Zealand birds are actually quite colourful given our temperate location. A fair point of comparison might be with England or Japan. Both island countries sit at similar latitudes to New Zealand in the Northern Hemisphere. Yet a casual skim through their respective bird guides suggests that our native birds are comparatively vibrant. Hihi, saddlebacks, tui and takahe are vividly coloured. But the introduced, British birds we can see out our windows (song thrush, dunnocks, chaffinches and house sparrows) aren’t going to win any feathered fashion contests.
Our native birds are also a bit more colourful than it may appear at first glance. For example, first appearances suggest that kaka and kea aren’t very colourful, especially considering that they’re both parrots, which can often be brilliantly coloured. But first appearances can be misleading. When both species are showing off to the opposite sex, they open their wings to display more brightly-coloured feathers hidden on the undersides of their wings. Perhaps hiding away more brightly coloured feathers until they are needed during the breeding season is a good way to avoid avian predators.
Another example of hidden colour is clearly exhibited by Kaka. Keen bird watchers will know that the tops of their heads are streaked with what appears to be whitish feathers. These reflect ultra-violet (UV) light quite strongly. Birds can see UV, but we cannot. So we can only imagine how colourful kaka appear to other birds.
Lastly, unlike European birds, many of our native species frequently pollinate flowers. Curiously, this in turn makes our birds temporarily more colourful. Tree Fuchsia pollen is vivid blue, kowhai pollen is bright yellow, flax pollen is orange and five-finger is white. The tree’s reproductive strategy involves coating bird feathers with pollen in the hope that some of it makes it to another flower. In the process, the bird’s plumage gets covered in ‘mutualistic make-up’, making them much more colourful during the flowering season.
So in the end, perhaps the absence of strikingly coloured birds in New Zealand can be attributed to lower bird diversity relative to the tropics. But if we dig a little deeper, I’m not sure we can say that New Zealand birds are dull. In fact there’s good reason to argue they’re actually far more colourful than their Northern counterparts.