The
Hawaiian duck (
Anas wyvilliana) or koloa is a
species of
bird in the family
Anatidae that is
endemic to the large islands of
Hawaii.
Taxonomically, the koloa is closely allied with the
mallard (
A. platyrhynchos),. It differs in that it is monochromatic (with similarly marked males and females) and non-migratory. As with many duck species in the genus
Anas, Hawaiian duck and mallards can interbreed and produce viable offspring, and the koloa has previously been considered an island
subspecies of the
mallard. However, all major authorities now consider this form to be a distinct species within the mallard complex. Recent analyses indicate that this is a distinct species that arose through ancient hybridization between mallard and
Laysan duck (
Anas laysanensis). The
native Hawaiian name for this duck is
koloa maoli (meaning "native duck"), or simply koloa. This species is listed as endangered by the
IUCN Red List of Threatened Species, and its population trend is decreasing.