Mariana Swiftlets recorded per
party hr on the Honolulu Christmas Count, 1944- 2007 (see Count
Page), indicating expansion of numbers after
introduction in the 1960s 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/