Prior to the arrival of the first Polynesian canoes nearly 1,500 years ago, Hawaii's natural wetlands provided habitat for resident and migratory waterbirds. Among the natural wetlands were forested bogs, streams, estuaries, lakes, and coastal marshes. Wetland mapping indicates that Hawaii (Region 32*) contains approximately 44,860 ha of wetlands and deep-water habitats, of which 81% are classified as palustrine scrub-shrub and forested habitats. These wetlands are located at mid- to high elevations as bogs and rainforest ecosystems. The USFWS estimates 9,100 ha of wetlands within coastal plains of Hawaii circa 1780. In 1990, the USFWS estimates 6,265 ha remaining, a decrease of 31%.
A total of 106 endemic species and subspecies of birds have been described from the Hawaiian Islands (Pyle 1988, Olson and James 1991). Of these, 35 became extinct before the arrival of Captain Cook in 1778, and an additional 23 since then, leaving 48 extant endemic taxa. The Hawaiian Islands historically supported a diverse array of waterbirds in wetland and forest habitats. During the past 2,000 years of human presence, all of Hawaii's endemic rails, flightless geese, and an ibis have become extinct (Olson and James 1982). This massive extinction is attributed to the impacts of humans and the plants and animals they introduced to Hawaii. Polynesian settlers and Europeans have both played significant roles in the alteration of Hawaiian ecosystems and the resulting extinction of species (Olson and James 1991).
The six extant species of endemic waterbirds are koloa maoli or Hawaiian duck, Laysan duck, 'alae 'keo'keo or Hawaiian coot, 'aeo or Hawaiian stilt, 'alae 'ula or Hawaiian moorhen, and nene or Hawaiian goose. All of these species are federally listed as endangered, have populations fewer than 3,000 birds, and require wetlands for survival (Engilis and Pratt 1993). Nearly 30 species of migratory ducks and geese and more than 30 species of migratory shorebirds have been recorded in the Hawaiian Islands (Pyle 1977). Among the most common species of migrant waterfowl are northern pintail, northern shoveler, lesser scaup, American wigeon, and Eurasian wigeon. These species use the island habitat for wintering, with the exception of resident mallard and fulvous whistling duck that have become established. Migratory waterbirds have shown a marked decline from tens of thousands in the 1950s to only a few thousand in the 1990s.
In the two centuries since the first European ships reached the islands, most of the wetlands have been degraded. As early as the 1850s, significant losses in wetland habitat began with conversion of wetlands to taro and then crops such as rice and sugarcane. More recently, urbanization of lowland, coastal areas, particularly on Oahu, has accelerated the conversion or alteration of wetlands. The coastal wetlands of Waikiki were drained in the 1920s and have been totally lost to development. Most degraded wetland systems have been filled or hydrological modified and are now occupied by hotels, houses, golf courses, shopping centers, landfills, military installations, highways, agricultural fields, and industrial sites (Griffin et al. 1989).
Introduction of exotic species has negatively impacted waterbird species. Exotic plants, such as California grass, Indian fleabane, pickleweed, and red mangrove present serious threats in many wetlands by out-competing more desirable native species and eliminating the interspersion of open water and vegetated areas. A major threat to the Hawaiian duck is hybridization with increasing numbers of resident feral mallards. The threat of hybridization is exacerbated on Oahu with severe reduction in wetland habitat and increasing numbers of mallard in lake and golf course areas. Introduction of the mongoose to control rats has resulted in a very serious threat to ground nesting birds. Only Kauai, Lanai, and Niihau are free of mongoose.
Protection and restoration of Hawaii's wetlands are essential to the recovery of the endemic waterbirds, as well as the migrant waterfowl and shorebirds. There are 476 ha of secured wetland habitat on Kauai, principally at Hanalei NWR (371 ha) and Huleia NWR (96 ha). Oahu has 708 ha of secured wetlands, principally at Kawainui Marsh (304 ha), Heeia Marsh (162 ha), and Kahuku Wetlands (57.5 ha), although all of these systems have been hydrologically altered. Maui/Molokai have 287 ha of secure wetlands, principally Kealia Pond NWR (202 ha) and Kanaha Pond (58 ha). The Big Island has some 30 ha secured, principally at Aimakapa, Kaloko, and Parker Ranch.
*Region 32 - Hawaii does not have a NABCI Bird Conservation Region Number
Continue Reading >>