Introduction

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 (1939, 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 separate the Flammulated Owl from other New World Otus species and ally it with Old World scops owls, although the phylogeny of this genus has not been subjected to cladistic or biochemical analyses.

Despite its small size, broad geographic range, and seeming abundance, the Flammulated Owl has a low reproductive rate. The species is apparently restricted to forests of commercially valuable trees, and timber management practices may influence its viability, although baseline population data are sparse and insufficient to model its population dynamics. In addition, virtually nothing is known about its range, habitat, or diet in winter.