THE BOREAL OWL AT THE SOUTHERN TERMINUS OF THE ROCKY-MOUNTAINS - UNDOCUMENTED LONGTIME RESIDENT OR RECENT ARRIVAL

Twenty-three Boreal Owls (Aegolius funereus) documented from April 198 7 to August 1993, including three fledged juveniles, unequivocally est ablish the species as a breeding bird in northern New Mexico where the y responded at a rate of 0.17 owls/survey hr during both breeding and non-breeding seasons. Their congener, the Northern Saw-whet Owl (A. ac adicus), was not recorded during the breeding season and responded at the rate of 0.03 owls/survey hr during the non-breeding season in the same areas. In mountain ranges apparently not occupied by Boreal Owls, Northern Saw-whet Owls responded at rates of 0.35 and 0.27 owls/surve y hr for breeding and non-breeding seasons, respectively. Potential ha bitat for Boreal Owls away from the Rocky Mountains was typically in i solated, small patches that likely would not sustain viable population s. Paleontological, archaeological, and late 19th-early 20th century a utumnal specimens from the southern Rockies support the hypothesis tha t the Boreal Owl has been present in Colorado and New Mexico for centu ries, possibly since the Pleistocene. They remained largely undocument ed because their high elevation sub-alpine conifer forest habitat is s nowbound during their most vocal period (February-April).