Adult Red-footed Boobies counted primarily at the Ulupau Head (KMAC) breeding colony, as recorded on the Honolulu Christmas Count, O'ahu, 1947-2014 (see Count
Page). Numbers show a decline from the 1950s
to the mid-1980s and then an increase into the 2010s. 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/