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

O'ahu, 1977-2007 (see Count Page), showing a peak in observations during the

1990s followed by a decline through the 2000s. Most observations of these ducks

after the 1990s were identified as hybrids with Mallard.

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/2009/