Red-vented Bulbuls recorded per party hr on the Waipi'o Christmas Count, O'ahu,
1977-2014 (see Count
Page), showing increases during
the 1970s and 1980s as populations were still expanding, followed by
fluctuating and possibly generally declining populations. 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/