The Northern Saw-whet Owl (NSWO; Aegolius acadicus) is a small, nocturnal owl, whose breeding and nonbreeding ranges have not been thoroughly established, in part because these limits are prone to yearly fluctuations (Cannings 1993). The NSWO is restricted to North America and breeds in the boreal and northern hardwood forest from the Maritime provinces and southern Quebec, across southern Ontario and the northern United States through the central prairie provinces to the Pacific coast; and from southeastern Alaska southward through the Rocky Mountains and other ranges at higher elevations to temperate forests in the central highlands of Mexico (Holt et al. 1999, Weidensaul 2015).

In Mexico, the NSWO is reportedly distributed on Pacific and Atlantic slopes, from the mountains of northeastern Sonora and Chihuahua, through the center of Mexico in the Trans-Mexican Volcanic Belt (TMVB) and...

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