History of endemic Hawaiian birds: Part I: population histories, species accounts: freshwater birds: Koloa-maoli

Abstract

Anas wyvilliana is a medium-sized (20" long) duck with variable mallard-like plumage. It was first described by P.L. Sclater in 1878. A total of 69 specimens are known world-wide in some 13 widely-scattered museums. Exhaustive search of literature, unpublished journals, and government reports uncovered some 3,006 observational notes, collection records, and related statements on relative abundance and geographical distribution from 1778 to 1982. Data are serially numbered, arranged in geographical and chronological order, referenced and systematically reviewed. Observers before 1900 recorded the Koloa as common and widespread, though becoming scarcer, in freshwater habitats on all of the major Islands. After 1903 there is a near-absolute 30-year gap of information on population status. Repeated surveys beginning in the 1940's have recorded successive population declines on Kaua´i, transient numbers on Ni'ihau, disappearance on O'ahu and Hawai´i, and extinction on Moloka´I and Maui. Release of some 853 captive-raised Koloa on O'ahu and Hawai'i from 1958 to 1980 has failed to establish clearly obvious self-sustaining wild flocks. It is concluded that relict numbers of this species on Kaua´i will continue to decline long-term and that restoration efforts, as presently known, will fail to effect re-establishment of self-supporting wild populations, except perhaps in token numbers.