The Hawaiian duck (Anas wyvilliana) or koloa is a species of bird in the family Anatidae that is endemic to the large islands of Hawaiʻi.

[3][4][5][6] Recent analyses indicate that this is a distinct species that arose through ancient hybridization between mallard and the Laysan duck (Anas laysanensis).

The koloa is most prominently found residing in the tall, wetland grasses and streams near the Kohala volcano on the main island of Hawaiʻi.

In any case, evolution has not moved fast enough for the species to reach reproductive isolation, since this interbreeding creates viable hybrids.

[18] Hawaiian ducks were found on the hottest coasts with suitable ponds as well as in the mountains that were up to 7,000 feet (2,130 m) high.

[20]" The Hawaiian duck was extirpated on all other islands, but was subsequently reestablished on Oʻahu, Hawaiʻi, and Maui through release of captive-reared birds.

In addition to predators, Kauai has experienced a loss of lowland wetland habitat, in turn affecting the Hawaiian ducks.

[12] Other conservation efforts for the Hawaiian duck include the development of "techniques for the identification of hybrids",[12] which in turn will result in "simultaneous genetic testing and morphological characterisation".

Since hybridization has been happening for an extended period of time, it is unlikely there are any pure individuals of the species left.

Efforts are underway to remove mallards from the islands in order to preserve the genetic diversity of the Hawaiian duck.

Predation threats to the koloa maoli include feral cats, rats, and small Indian mongooses, which eat the eggs and young.

[16] The previous hunting of water birds in these area from 1800s to the 1900s also played a major role in the decline of this species.

Urban development along with loss of their natural habitat due to the use of the land for local agriculture plays a major role to the indefinite decline of this now endangered species.

In the late 1800s, the mallard, also known as Anas platyrhynchos, were flown in to stock up the ponds of Hawaiʻi for ornamental purposes, but soon enough they were massively imported throughout the 1950s and the 1960s.

Several attempted reintroductions have already failed due to the hybrid ducks produced in captivity faring badly in the wild.

[24] The "conversion of flooded taro fields to dry sugar-cane acreage" destroys parts of this species' habitat.

The Hanalei National Wildlife Refuge makes this all possible for the Anas wyvilliana to procreate when their habitat is not suitable for their survival.

It is an ongoing issue that requires constant attention, the more accurate the research is, the better of an idea we have of where money should be spent to help the Hawaiian duck survive.

Other conservation plans include plans to "obtain public acceptance of feral duck control", "continue protection and restoration of important wetland habitats", and "develop alternative predator control methods and explore the use of predator fences.