Distribution in the Americas
The distribution of the Ferruginous Pygmy-Owl spans across both continents of the Americas. The northernmost populations inhabit southern Arizona, southern Texas, and the central Sonora desert in Mexico (Proudfoot et al. 2006a; Flesch and Steidl 2007; Flesch and Steidl 2006). The distribution extends south through the regions bordering the Pacific and Atlantic coast of Mexico (Flesch and Steidl 2006, Flesch and Steidl 2010). Further south in Central America, Glaucidium brasilianum ranges through Belize, Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, and Panama (Proudfoot and Johnson 2000). In South America, Ferruginous Pygmy-Owls can be found in north and southeast Colombia, Venezuela, Margarita Island, Trinidad, and east of the Andes in Ecuador, Peru, Bolivia, Brazil, Paraguay, Chile and Argentina (Proudfoot and Johnson 2000).
The upper elevational limit of Ferruginous Pygmy-Owl is 1400 m in Mexico (Howell and Webb 1995); 1500 m in Costa Rica (Stiles and Skutch 1989); to at least 1000 m in Colombia (Hilty and Brown 1986) and Venezuela (Hilty 2003), although locally to 1900 m in Aragua, northern Venezuela (Hilty 2003); to 500 m in Ecuador (Ridgely and Greenfield 2001); locally to 2000 m in Peru (Schulenberg et al. 2007) but usually much lower, e.g. to 1000 m in southern Peru (Walker et al. 2007); and to 1500 m (locally to 2300 m) in Bolivia (Hennessey et al. 2003).
The Ferruginous Pygmy-Owl prefers lowland habitat ranging from hot, arid desert scrubland (Flesch and Steidl 2006) to the edge of humid tropical forests (Flesch and Steidl 2010). In a 2003 study, Borges et al. compared habitat use by several species of owls, including G. brasilianum, in two forest types in Jaú National Park, Brazil: terra firma forests (unflooded) versus igapó forests (black water-flooded). They found the species only in igapó forests, which are characterized by low canopy heights and relatively low diversity of flora (Borges et al. 2004). Ferruginous Pygmy-Owls occur in undisturbed habitat as well as in or around human settlements, from small villages to large cities (Proudfoot and Johnson 2000).
The range has contracted somewhat at the distributional limits of the species in the southwestern United States. Whereas Ferruginous Pygmy-Owl once was numerous and widespread in Arizona, it is now only observed in several disconnected locations in the state (Flesch and Steidl 2006, Johnson et al. 2003). Johnson et al. contend that the species began its decline as early as the 1920s (not in the 1950s as was previously thought), and that the causes of its decline are primarily biogeographical changes brought on by anthropogenic activity. Examples include significant losses of riparian vegetation due to grazing, woodcutting, and urbanization, and to the systematic ecosystem restructuring accompanying damming projects along the Salt River from the early 1900s to 1930s (Johnson et al. 2003). Trends in Texas follow a similar profile (Flesch and Steidl 2006).