"pure" Hawaiian ducks are still only found on Kauaʻi. With an approximate population of 2,200 birds (Engiiis and Pratt 1993, Engilis et al. 2002) This consists of 2,000 on Kaua`i and 200 on Hawai`i. However, these ducks are in decline due to hybridization. They are also vulnerable to predators because of the low location of their nests on the ground. This makes it easier for predators such as cats, pigs, dogs, and mongoose to attack them. In addition to predators, Kauai has experienced a loss of lowland wetland habitat, in turn affecting the Hawaiian ducks. Conservation status Wildlife refuges including Hanalei National Wildlife Refuge on Kaua'i are essential breeding areas for Hawaiian Ducks (Todd 1996) The species was reintroduced to O’ahu between 1958 and 1982. In 1989, twelve of these captured birds were released on the island of Maui. The species was also reestablished on the island of Hawai'i between 1976 and 1982 (U.S. Fish and Wildlife Service 2005). Throughout the 1980s, the importation of Mallards to Hawai'i was limited in an effort to reduce hybridization with Hawaiian Ducks. (Uyehara et al. 2007) Other conservation efforts for the Hawaiian Duck include the development of “techniques for the identification of hybrids” (Uyehara et al. 2007), which in turn will result in, “simultaneous genetic testing and morphological characterisation” (U.S. Fish and Wildlife Service 2005). Hybridization Hybridization is arguably one of the most serious but overlooked threats to the Hawaiian duck, specifically interbreeding between Hawaiian ducks and feral mallards. Since hybridization has been happening for an extended period of time, it is unlikely any pure versions of these species are left.[3] “Determination of the population status of Hawaiian ducks and whether there are any pure Hawaiian ducks left on O`ahu will require simultaneous genetic testing and morphological characterization to develop reliable morphological criteria for distinguishing Hawaiian ducks, female mallards, and hybrids. Once such criteria are available they can be used to identify birds for removal in order to reduce interbreeding and introgression.”[3] It has been shown that offspring between mallards and the Hawaiian duck produce fertile offspring. It has also been shown on Kauai that breeding Hawaiian duck/mallard crosses with Hawaiian ducks over time reduces the expression of the mallard genes showing promise to restoring the natural population. Efforts are underway to remove mallards from the islands in order to preserve the genetic diversity of the Hawaiian duck. Other factors influencing population The