The Laysan Duck (Anas laysanensis) is a dabbling duck which is native to Laysan Island, Hawaii. This duck is related to the Mallard, and has sometimes been considered to be an island race of that species. It has been determined, however, that it is not as closely related, but rather is a sister taxon to the Mallard and its closest relatives.
Subfossil remains found on the major southeastern Hawaiian islands have been determined to belong to this species; it became extinct everywhere except on Laysan before European contact due to hunting and introduced predators, whereas the more adaptable Hawaiian Duck still survives in somewhat larger numbers.
This small brown duck has a darker head and a white eye patch and the wings are whitish below, and dark above. The legs are orange. The male of this species shows a white-bordered green speculum in flight, whereas the female has a less obvious brown speculum. Also, the colors on the female’s head are somewhat less defined. The male and female have calls similar to the Mallard.
Laysan Island is a mere 3km long and the population of this duck is based on the central saltwater lagoon located there. It feeds mostly by picking plant food as it walks, mainly in the evening or at night. Another favorite food is brine flies, which are very abundant around the lagoon; the ducks walk through resting flies on the shore to startle them and then simply grab them by the beakful as they rise up.
This duck nests on the ground under bushes near the lagoon, and is social outside the breeding season.
This is a tame species and its population was reduced to perhaps as few as seven birds by 1912 due to shooting by guano miners and plumage collectors, and introduced rabbits which all but destroyed the vegetation on the entire island. One clutch of the last female found at that time was destroyed by a Bristle-thighed Curlew.
Protection, eradication of the rabbits, and captive breeding have since restored the numbers to about 500 ducks, about the maximum this tiny island can support. It is considered critically endangered, because its population can fluctuate between about 150 and 500 individuals, over the course of a period of several years, depending on weather conditions and availability of food in the breeding season. If predators or a disease were accidentally introduced to the island (e.g. by a shipwreck) at a point where the population is low, the species would probably be wiped out in the wild. Captive populations have been established to act as a reserve, should such a case occur.