The kakapo, a bird that lives in New Zealand, is not designed for survival. Weighing up to 4 kilograms, it is the world's fattest parrot. It mates (交配)only when the rimu tree is in fruit, which happens every few years. It developed gradually in the absence of land-based natural enemies, so instead of flying above the trees it walks like a duck across the dry forest floor. When it moves unsteadily across something that might kill it, it will stand still.
Such unusual characteristics turned it into fast food for human settlers, and for the cats and rats they brought with them. It seemed to have disappeared by the 1970s, until scientists came across two undiscovered populations in the country s south. These survivors were eventually moved to small enemy -free islands, where researchers have spent decades trying to get them to breed (繁殖).
The scientists' patience is finally rewarded. The rimu was in fruit this year, and more than 80 chicks hatched, making this the best breeding season, on record. Many have survived into adolescence, increasing the number of adult kakapos by a third, to 200 birds.
Another danger to the kakapo is a lack of genetic diversity. This is one reason why fewer than half of kakapo eggs hatch. By arranging the genome (基因组) of every living bird, scientists can identify closely-related individuals and put them on different islands. Every bird is fitted with something to track its slightest movement. If a female mates with an "unsuitable" male, the process can be stopped.
All these efforts cost almost New Zealand $1 .3 million this breeding season. Yet the kakapo's future still looks unsafe. Earlier this year a severe disease tore through the population. And tiny as the number of kakapos is, space is running out on the two islands where most of them live. New enemy-free settlements must soon be found.
