Hawaiian Ducks (Koloa) recorded per party hr on the
Honolulu Christmas Count, 1944-2014 (see Count
Page), showing a slight increase in
observations during the 1970s-1990s, due to re-propogation
programs, followed by a decline through the 2000s and a large increase
after 2008. Most observations of these ducks after the 1990s were
identified as hybrids with Mallard. 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/