Introduction

Whiskered Screech-Owl. Madera Canyon, AZ. December.

Figure 1. Distribution of the Whiskered Screech-Owl

The Whiskered Screech-Owl, formerly called Spotted Screech-Owl and Whiskered Owl, inhabits montane woodlands and forests at 1,000–2,900 m from southeastern Arizona and adjacent New Mexico to northern Nicaragua. Bristles on the ends of its facial-disc feathers (“whiskers”) give it the name trichopsis, meaning hairy appearance, but are difficult to see. The adult’s golden to orangish iris, buffy to rusty plumage tones and throat patch, and uniquely trilled songs are better field characteristics. Most individuals are gray with a rusty hue, but a rufous morph occurs, mainly in Latin America in shady, cloudy mountain forest—similar to the Eastern Screech-Owl’s (Megascops asio) rufous morph in frequently overcast climates.

Whiskered Screech-Owls are secondary-cavity nesters and usually the most abundant owls in optimum habitat, reaching nesting densities of 11 pairs/km²in canyon riparian forest at 1,500–1,750 m. They are permanent residents coexisting with as many as 15 other avian cavity nesters, including other screech-, Elf, and pygmy-owls, woodpeckers, trogons, and songbirds. Like all U.S. screech-owls, Whiskereds are polyterritorial, defending alternative nest cavities. They sing to advertise the sites, beginning in late January; lay 2–4 eggs in March to May; and fledge owlets about 50 days later. One familiar song is a Short Trill of few notes, the last 1 or 2 often on a lower pitch. Another is the Telegraphic Trill 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 as important prey are partly replaced by beetles, especially June bugs, during the climatic shift from warm, dry spring to cooler, wetter summer in Sierra Madrean habitats. Unless unduly disturbed, Whiskered Screech-Owls capture insects attracted to lights in suburbanized canyons and nest successfully along roads in campgrounds, next to houses, and in coffee fincas. They are unaggressive toward noninterfering avian associates and other animals, including humans, but warn of predators with Barks and defend offspring with dives and rare physical attacks.

The species was first discovered in Mexico in 1832, but its type locality is unknown (restricted to southwestern Puebla by Moore and Peters 1939) and the type specimen lost (van Rossem 1932). In 1891, Whiskered Screech-Owls were found in the Huachuca Mountains of Arizona, the earliest published U.S. report (Brewster 1898), although collected and misidentified as Megascops (Otus) asio in the Santa Catalina Mountains of Arizona in 1885. Originally, they were considered summer visitors in the U.S. (Swarth 1914). The first eggs were found in the Huachucas in 1901 but remained unrecognized until 1937, because the species was confused with O. asio (Bendire 1892, Gilman 1909, Brandt 1937), then including the Western Screech-Owl (M. kennicottii).

Published information is scanty and often incorrect, so we rely on personal observations in Arizona, New Mexico, and Mexico since 1955, indicated as FRG-NYG only where needed for clarification. Most data are from Cave Creek Canyon, Chiricahua Mountains, and Ramsey Canyon, Huachuca Mountains, Arizona, 1995–1999, unless indicated otherwise. Time is Mountain Standard. Spear-man rank correlation coefficients (rs) are used. Significant and insignificant mean in the statistical sense of less than or greater than 5% probability of error, respectively. Unreferenced interspecific comparisons are from Gehlbach 1981, 1994, 1995a, 1995b, 1996, Gehlbach and Baldridge 1987, McCallum and Gehlbach 1988, McCallum 1994, McCallum et al. 1995, Henry and Gehlbach 1999 .