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Vol.18, no.2
April/May 2015


The Little Duck that Might 
Story By: Rachel Davies

2015 is shaping up to be a big year for an independent little brown duck called the koloa maoli. Otherwise known as the Hawaiian duck or Anas wyvilliana or simply the koloa, it’s an endangered species with an estimated population of two thousand—and even with all of those names, most people have never heard of it. “When I tell people I’m working with the Hawaiian duck,” says Oregon State University PhD student Christopher Malachowski, “they say, ‘Oh! The nene!’”—confusing the duck with the Hawaiian goose. Almost everyone who works with the koloa can tell a similar tale, but they don’t mind. “I have a soft spot in my heart for little brown birds that nobody pays attention to,” says Kim Uyehara, biologist at the Hanalei National Wildlife Refuge on Kaua‘i. “People see it out on the marsh, and they can’t really connect to it,” says Andy Engilis, longtime champion of the koloa. “But if you’ve ever held a Hawaiian duck, they’re a very charismatic little bird.”

If you’re ever lucky enough to hold a koloa, you’ll have your arms around a tidy dabbling duck about two-thirds the size of a mallard, with a small beak, sparkling eyes and rich, deep brown plumage (though its coloring does vary subtly with its stages of life and by gender). The koloa once lived on all the Hawaiian islands and could be found anywhere from sea level to ten-thousand-foot elevation; the duck is an expert at navigating the steep valleys and lush forests found deep in the seclusion of Hawai‘i’s mountains. In fact, the koloa is so private that it’s only in the last decade that we’ve been able to learn much about it.

The qualities that have kept the koloa out of the public eye—its shyness, its swift departure whenever a perceived threat comes near, its precocious attitude—have been key to its survival in an environment in which most other endemic waterfowl are now extinct. Just a couple of thousand years ago in Hawai‘i, the koloa rubbed feathers with a marvelous collection of fellow duck species, all of them having evolved in the seclusion of the Islands, which were then free of any mammalian predators. Fossils unearthed in the Makauwahi Cave on the south coast of Kaua‘i comprise about a dozen unique duck species in total, including a flightless duck as large as a goose that grazed on grasses much like a cow or sheep; a nocturnal, mole-like duck; and a duck with a wide, deep bill akin to the jaw of a tortoise. Yet the only duck to have survived the coming of man to the main Hawaiian Islands is the secretive koloa. Farther north the Laysan duck (A. laysanensis) survives on the atolls of Midway, Laysan and Kure. Both species have barely squeaked through, with their populations dwindling perilously low at points over the last century.

The threats to the koloa are by no means over. One of the most significant today is the threat of genetic extinction through crossbreeding with mallards, a duck introduced to Hawai‘i in the 1800s. With crossbreeding, over time the koloa would gradually become koloa/mallard hybrids until no pure koloa remained. Such an extinction would be largely invisible because the koloa’s plumage looks mallard-like at different points in its life—so much so that even experts cannot always be 100 percent sure whether a duck is a hybrid or pure koloa. Another danger is avian botulism, a paralytic neurotoxin that infects maggots, which ducks are fond of eating; pond stagnation, as well as possible climate change-driven warming of pond waters, is creating conditions in which massive outbreaks of the fatal disease can occur. Other hurdles to the koloa’s survival include loss of wetland habitat; introduced predators like mongooses, cats and rats; and various invasive fishes and weeds that destroy the bird’s food source.

Happily the koloa has a stronghold at the Hanalei National Wildlife Refuge on Kaua‘i, an island without an established mongoose population and with fewer introduced mallards, and it’s estimated that around half of the world’s koloa population calls the refuge home. “This is probably the most important site in the world for koloa,” says Uyehara, squinting at the mosaic of managed ponds glistening in the morning sun that she and the team work hard to maintain. The refuge is a picturesque expanse of 917 acres of green wetlands, taro fields, rivers and streams flanked by the steep, jagged mountains that run inland from the one-lane bridge heading to Hanalei bay. The refuge benefits more than just the koloa—several endangered birds thrive here. As koloa flap fast and sleek overhead, ‘alae kea (Hawaiian coots) and ae‘o (Hawaiian black-necked stilts) splash about in the ponds, ‘alae ‘ula (Hawaiian common moorhens) call to each other from the low sedge, while on the road to the refuge’s office, nene wander curiously alongside cars, examining tires and sniffing paintwork. Where else in the world can you see five endangered birds on one stretch of road?

The refuge has a tiny staff as well as two interns and a research assistant. The team lays and checks traps for predators, repairs fences, studies the birds and maintains the hundred acres of managed ponds, swamps, channels and openings that constitute the birds’ wetland homes. They also monitor avian botulism; refuge staff estimate they were losing one koloa every other day when the outbreaks were at their worst. They are working around the clock consulting soil specialists, ecologists and disease experts to discover what is triggering the outbreaks.

To keep the ponds as healthy as possible, the refuge employs an ingenious scheme of draining and refilling them, adjusting the water level to suit the birds’ needs, encourage native plant growth and manage invasive weeds. After a year or two, once a pond is choked with California, paspalum and guinea grasses—aggressive weeds that grow even by moonlight—it is drained and the soil is reconditioned with heavy machinery.