By Jan TenBruggencate
Advertiser Columnist

Hawai'i's state bird, the nene, or Hawaiian goose, suffered a severe decline in population between 1100 and 1750 — probably as a result of human activity — and lost much of its genetic variability as a result.

Genetic variability is considered an important factor in whether a species will be able to survive diseases and changes in environment.

Loss of variability can leave species more vulnerable to threats, and less able to rebuild populations.

Breeders often seek to bring in genetic material from distant branches of a species to broaden the genetic variability of offspring, whether they are dealing with crops, pets or endangered species.

According to researchers from the Smithsonian Institution and the University of California at Los Angeles, genetic tests show that while the nene population fell to less than 30 birds in the mid-1900s, their loss of genetic variation occurred much earlier.

The authors of the article in the June issue of Science magazine set out to determine whether the nene's loss of genetic variability was the result of a population crash or a long-term consequence of being stranded on relatively small islands.

Citing the work of bird fossil experts Storrs Olson and Helen James, who have done considerable work identifying now-extinct Hawaiian birds, they compared DNA from modern nene, museum specimens and fossil bones collected from sites as old as 2,500 years, long before humans arrived in the Islands.

Their results suggest the nene lost its genetic variability during the same period when early Hawaiian populations were rising and residents were expanding settlements from the most favorable coastal and valley regions into "marginal ecological zones."

Other species declined at the same time. On Kaua'i, at least five other ground-dwelling birds became extinct, and the nene disappeared, although it survived on the Big Island.

"Ecological changes associated with human settlement are assumed to have caused the extinctions, and apparently caused a dramatic reduction in genetic diversity in the nene on Hawai'i as well," the authors write.

Why did the bird survive at all? The authors surmise that perhaps Hawaiian land clearing created new habitat, or chiefs banned the taking of the birds, which could have been domesticated along with chickens, dogs and pigs.

The scientists said other island species — even if they have survived — may suffer similar genetic changes as the result of competition with humans.

Jan TenBruggencate is The Advertiser's Kaua'i bureau chief and its science and environment writer. You can call him at (808) 245-3074 or e-mail jant@honoluluadvertiser.com.