Pygmy-owls (Glaucidium) are very small owls, with a large rounded head, a pair of prominent black marks (false "eye spots") on the nape, and a relatively long tail. Colima Pygmy-Owl is a small species of Glaucidium. The upperparts are brown, with small white spots on the crown; the underparts are white, with cinnamon to buffy brown streaks.
Colima Pygmy-Owl overlaps geographically with two other species of pygmy-owl, Ferruginous Pygmy-Owl (Glaucidium brasilianum) and Northern Pygmy-Owl (Glaucidium gnoma). Colima Pygmy-Owl is slightly smaller than Northern, with a shorter tail with fewer pale transverse bars on the tail (3-4, versus 5-6 bars on the tail of Northern), and has a different voide. Colima generally occurs at higher elevations than Ferruginous, which also is larger and longer tailed, often is brighter rufous brown, has 6-7 pale bars on the tail, and its crown is narrowly streaked (not spotted).
The following description is based on Ridgway (1914) and on Howell and Webb (1995):
Adult: Sexes similar. Crown drab brown, thickly sprinkled with small dull white spots. Nape with typical Glaucidium "false eyes" pattern of two large blackish spots, outlined with a narrow pale cinnamon buffy border. Back, rump, scapulars and wing coverts brown, the scapulars suffused marginally with pale cinnamon buff. Median wing coverts with a few large terminal buffy white spots; some of the greater wing coverts also edged terminally or subterminally with buffy white. Secondaries crossed by four or five narrow dull cinnamon buff bands. Primaries darker grayish brown, outer webs very indistinctly spotted with paler brown. Rectrices deep grayish brown, crossed by 3-4 transverse series of oval white spots. Narrow dull white supercilium. Underparts dull buffy white; sides of breast light cinnamon brown, belly broadly streaked with cinnamon brown.
Juvenile: Crown and nape gray and unspotted, contrasting with brown back. Forecrown may be flecked with whitish to buff. "False eyes" may be sootier, the cinnamon nape band lacking or indistinct, and the pale bars on the rectrices may be buffy cinnamon.
Bill and cere: yellowish horn
Toes: pale yellowish
Bare parts color data from König and Weick (2008).
Total length: 13-15 cm (König and Weick 2008), 14-15 cm (Howell and Webb 1995)
Linear measuments (from König and Weick 2008):
male (n = ?)
wing length 81-85 mm
tail length 51-54 mm
female (n = ?)
wing length 84-88 mm
tail length 53-56 mm
Mass: male 43-48 g (n = ?; König and Weick 2008), female "heavier" (König and Weick 2008)