The Whiskered Screech-Owl inhabits montane forests at 1,000–2,900 m elevation from southeastern Arizona and adjacent New Mexico south to northern Nicaragua. Bristles on the ends of facial feathers give it the name trichopsis, meaning hairy appearance, but these “whiskers” are difficult to see. Better field characteristics are the uniquely trilled songs, orange-tinged irides of the adult, and a buffy tinge to the plumage and throat patch. Most individuals are gray with a faint rusty hue, but a rufous morph occurs, mainly in Latin America in shaded cloud forest—similar to the prevalence of the rufous morph Eastern Screech-Owl (Megascops asio) in frequently overcast climates.
The Whiskered Screech-Owl is a secondary-cavity nester and usually the most abundant owl species in optimal habitat, reaching nesting densities of 11 pairs/km2 in canyon riparian forest at 1,500–1,750 m. They are permanent residents coexisting with up to 15 cavity-nesting bird species, including other screech-owls, pygmy-owls, Elf Owl (Micrathene whitneyi), woodpeckers, trogons, and songbirds. Like other screech-owls in the U.S. and Canada, the Whiskered Screech-Owl is polyterritorial, defending alternative nest cavities. They sing to advertise the cavity sites in late January, lay 2–4 eggs from March to May, and fledge owlets about 50 days later. The short trill is a familiar song, a short series of few notes, the last 1 or 2 often on a lower pitch. Another is the telegraphic trill, a series of long and short notes resembling Morse code.
Insects, including caterpillars, are primary foods, but the diet incorporates a variety of arthropods, lizards, snakes, birds, bats, shrews, and mice. Moths are important prey, but are partly replaced by beetles (especially June bugs) as warm, dry spring weather transitions to the cooler, wetter summer in the Sierra Madre Mountains. Unless unduly disturbed, the Whiskered Screech-Owl captures insects attracted to lights in suburbanized canyons and nest successfully along roads in campgrounds, near houses, and in coffee fincas. The species is generally not aggressive toward avian associates and other animals, including humans, but when necessary will warn of predators with bark calls and defend offspring with dives, and rarely physical attacks.
The Whiskered Screech-Owl was first discovered in Mexico in 1832, but the exact type locality is unknown (restricted to southwestern Puebla by Moore and Peters 1939), and the type specimen was lost (Van Rossem 1932a). In 1891, the species was found in the Huachuca Mountains of Arizona, the earliest published U.S. report (Brewster 1898b), although the species was collected and misidentified as Megascops (Otus) asio in the Santa Catalina Mountains of Arizona in 1885. Originally, the Western Screech-Owl was considered a summer visitor to the U.S. (Swarth 1914a). The first eggs were found in the Huachuca Mountains in 1901, but remained unrecognized until 1937, because the species was confused with Megascops (Otus) asio (Bendire 1892b, Gilman 1909c, Brandt 1937), which then included the Western Screech-Owl (M. kennicottii).
Published information on the Whiskered Screech-Owl is scant, so this account relies on personal observations in Arizona, New Mexico, and Mexico since 1955. Most data are from southeastern Arizona (1995–1999) at Cave Creek Canyon in the Chiricahua Mountains, and at Ramsey Canyon in the Huachuca Mountains. Unreferenced interspecific comparisons are from Gehlbach 1981, Gehlbach 1994c, Gehlbach 1995a, Gehlbach 1995b, Gehlbach 1996, Gehlbach and Baldridge 1987, McCallum and Gehlbach 1988, McCallum 1994, McCallum et al. 1995, and Henry and Gehlbach 1999.