Hawaiian native bird expert Renate Gassman says introduced predators (from tree-climbing rats to feral cats) have taken their toll on indigenous species like the i"iwi.Jim Motavalli
The first human colonizers found 140 native breeding bird species in Hawaii, many of them found nowhere else, but half of them are now extinct. According to state accounts, 71 species remain, and 32 are federally listed, 15 of them either extinct or on the edge, with less than 500 individuals remaining. In fact, Hawaii has more endangered species than any other U.S. state.
Renate Gassman is a German-born bird veterinarian who has worked with Hawaii’s critically endangered crow, the "alala. (Captive breeding efforts are underway, but only two "alalas remain in the wild.) Gassman, who leads birding tours, says that Hawaii’s native species fell victim to many predators, beginning with the rats that stowed away in canoes with early Polynesian settlers.
Tree-climbing rats feast on bird eggs, and further damage is done by feral cats, pigs, goats, dogs and mongooses—all introduced species. The islands" biggest native mammal is the hoary bat. Alien species introductions continue at a rate of 20 per year, slipping through on airline flights, in the mail and as ship cargo. In contrast, scientists say new species are introduced naturally in Hawaii only once every 10,000 years.
Deforestation was also a factor in bird declines. By 1890, 80 percent of all native forest had been logged. Even more ominously, global warming is pushing mosquito populations into the higher elevations, threatening native bird populations with avian malaria.
Hawaiian wildlife managers work with nonprofit groups to cull ferals, a tactic that has sometimes put them at odds with animal rights activists. People for the Ethical Treatment of Animals (PETA), for instance, has opposed efforts by The Nature Conservancy (TNC) to snare and kill Hawaii’s feral pigs.
Former federal wildlife official Sue Daniels says, "I agree with many of PETA’s positions. However, when extinctions and severe endangerment result from introduced species, I believe the non-native animals must be removed as humanely as possible. This is precisely what TNC is doing in Hawaii." PETA advocates live trapping and using birth-control methods.
In Hosmer Grove, a natural gorge puts visitors at eye level with the tree canopy, making both visual and auditory contact with the i"iwi. These bright red rainforest honeycreepers have long, curved bills that are ideally suited for sipping nectar from Hawaiian lobelias. But these plants, too, are endangered.