A breeding pair of nene or Hawaiian geese (Branta sandvicensis), the state bird of Hawaii, absent from the island of Oahu for hundreds of years, has been found nesting there to the delight of wildlife biologists. The nene descended from Canada geese that arrived in Hawaii almost 1 million years ago shortly after the islands were formed. The species name sandvicensis refers to the Sandwich Islands, the name by which the Hawaiian Islands were known previously. Mitochondrial DNA found in fossils indicates that all species of Hawaiian geese, living and extinct, are closely related to the Giant Canada Goose (B. c. maxima) and Dusky Canada Goose (B. c. occidentalis).

Though the nene was quite common throughout the islands during the time of Captain Cook’s explorations in 1778, hunting and introduced predators, like Small Asian Mongooses, cats and pigs reduced the population to 30 birds by 1952. The expansion of agricultural cultivation by Polynesian settlers and subsequently unrestricted hunting by European colonists, in addition to habitat encroachment brought the nene near to extinction. With focused conservation and breeding programs, the number has increased to 2,000, mostly on the island of Kauai. Breeding pairs have periodically been airlifted to the Big Island and Maui, though according to the U.S. Fish and Wildlife Service, this pair on Oahu flew there on their own and hatched three goslings. As an endangered species and Hawaii’s state bird, the discovery of the nene nesting on Oahu Island is significant.

The nene has the smallest range of any living goose and remains sedentary and isolated. A terrestrial bird, the nene has adapted to life on islands with limited fresh water habitat. They are taller and more upright than many geese of similar weight, and thus can reach high to gather fruit, seeds and foliage. Their legs and padded toes with reduced webbing are long and strong, and they able to swim well, but adept at walking and running over rugged terrain. Nene use freshwater habitats but unlike many waterfowl, they do not require either oceanic or freshwater habitat. Though its ancestors arrived on the islands after flying across the ocean, the contemporary Hawaiian geese have wings reduced in size. They will fly from island to island but will not attempt longer flight.

The fossil record suggests that 11 species of waterfowl evolved in the Hawaiian Islands. The endemic Hawaiian anatids are an unusual group of waterfowl since many were flightless and many, like the nene adapted to the terrestrial landscape of the islands. The nene, the Hawaiian Duck (Anas wyvilliana), and Laysan Duck (A. laysanensis) are the only survivors, though all are included on the Hawaii and U.S. Fish and Wildlife Service lists of Endangered Species. With its agile and powerful legs, the Hawaiian Goose has adapted to shrublands and grass lands but flourishes also in areas altered by human presence. They are also found in coastal and subalpine habitats. Fossil remains suggest a wider range in the past.

As frequently with terrestrial waterfowl, they build nests on the ground and lay small clutches of large eggs. Goslings mature slowly and have poor survival rates. Nene evolved with aerial predators and both eggs and young are frequently prey to introduced mammals. On the southern islands and Maui, nene nest, forage and raise goslings in grassy shrub land and on lava flows with sparse vegetation. Overall the Hawaiian goose suffers low productivity notably on Maui at mid and high elevations. The diets of nene living in wild areas are low in protein. On Kauai there are more nutritious food sources and fewer predators. In managed grasslands and where supplemental food is available, the nene has been more successful at maintaining populations. The discovery of the nene nesting on Oahu Island has drawn lots of attention since it is both an endangered species and Hawaii’s state bird.

By Lawrence Shapiro

Sources:

Earthweek

Birds of North America

PLOS

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