Editor's Note: —Formerly placed in the genus Otus, this species has recently been assigned to Psiloscops, owing to its genetic, vocal, and morphological differences from other Otus owls. See the 54th Supplement of the AOU Checklist for details. Future revisions of this account will adjust for this change.
The Flammulated Owl, a tiny owl with a deep voice and small clutch size, is perhaps the most common raptor of the montane pine forests of the western United States and Mexico. It subsists almost entirely on insects, especially moths and beetles, and appears to be highly migratory, at least in the United States and Canada. First described in 1859 by J. J. Kaup, it was widely considered rare until observers, following Marshall ( Marshall 1939 , Marshall 1967 ), began imitating calls to incite vocal responses by territorial males.
Specialized syringeal anatomy in these small birds (males < 60 g) produces hoarse, low-frequency notes sounding like those of much larger owls. Such calls are difficult to locate, enhancing the illusion that a large bird is calling from a distance. Song delivery and morphological features ally the Flammulated Owl with Old World scops owls of the genus Otus, but recent cladistic analyses support reevaluating this taxonomic association and establishing a new sister-group relationship between Flammulated Owls and the New World screech-owls of the genus Megascops (Proudfoot et al. 2007).
Despite its small size, broad geographic range, and seeming abundance, the Flammulated Owl has a low reproductive rate, and data from Colorado suggest that at least some males exhibit delayed reproduction. The species is primarily associated with forests of commercially valuable trees, and timber management practices may influence its viability, although baseline population data exist only for one area in Colorado (Linkhart and Reynolds 2006, 2007) and New Mexico (Arsenault et al. 2005) and are insufficient to model its population dynamics. In addition, virtually nothing is known about its range, habitat, or diet in winter.