The flightless Hawaiian bird related to ducks that went extinct after human arrival was the moa-nalo.
Moa-nalo was the name for a group of large, flightless, goose-like ducks that evolved on several Hawaiian Islands. They lived on Kauai, Oahu, Maui, Molokai, and Lanai, but not on the island of Hawaii itself. Their remains were discovered as subfossils in places such as sand dunes, caves, lake beds, sinkholes, and lava tubes.
Ancient DNA showed that moa-nalo were more closely related to dabbling ducks, including the mallard lineage, than to geese such as the living nēnē. They became major herbivores in Hawaii, feeding on vegetation. Several species had unusual bills: some had heavy, tortoise-like jaws, while others had serrated structures called pseudoteeth.
Moa-nalo disappeared before James Cook’s arrival in 1778, probably after Polynesian settlement brought hunting, habitat changes, and introduced predators. A common mistake is to equate them with the New Zealand moa; despite the similar name, moa-nalo were specialized Hawaiian waterfowl.