Hawaiian Ducks (Koloa) recorded per party hr on the Waipi'o Christmas Count,

O'ahu, 1977-2014 (see Count Page), showing peaks in observations during the

early 1990s and early 2010s Most observations of these ducks after the 1990s were identified as hybrids with Mallard but they all refer to the same populations of partially introgressed Koloa.

Species account

Graphs of Christmas Count data developed as part of The Birds of the Hawaiian

Islands: Occurrence, History, Distribution, and Status by Robert L. Pyle and Peter Pyle http://hbs.bishopmuseum.org/birds/rlp-monograph/