Tom Lake of the Hudson River Almanac informed me that White Pelican sightings on the Hudson River are rare but not unheard of. According to Tom, White Pelicans are seen about about once every 5 years. The last recorded sighting in the Hudson River Almanac white pelican was May 3, 2004 at Kingston:
“We spotted a white pelican sharing a jetty with assorted gulls at the mouth of the Rondout at Kingston. This is a very unusual sighting and one that is often made in spring, at the changing of the seasons, when migrating white pelicans can be blown off course by nor’easters.” –Bill Drakert, Fran Drakert
Tom also pointed to a couple of White Pelican sightings in the spring of 1994 (Hudson River Almanac I:12,18).