Higher reversed sexual size dimorphism among nesting pairs of Northern Pygmy-Owls (Glaucidium gnoma) in northwestern Oregon than among specimens collected at the range-wide scale

I report on the strength of reversed sexual size dimorphism (RSD) in a local sub-population of Northern Pygmy-Owls (Glaucidium gnoma) in northwestern Oregon (2007–2012) in comparison to range-wide museum specimens examined by Earhart and Johnson (1970). Using Storer's Dimorphism Index (DI), RSD was higher among local breeding pairs (DImass = 6.64, DIwing = 4.90, n = 20 pairs) and among all local specimens (DImass = 6.20, DIwing = 4.39, n = 31 females, n= 23 males) than for specimens range-wide (DImass = 5.45, DIwing = 4.30, n= 10 females, n= 42 males). RSD was also more distinct locally, because mass alone was diagnostic of the sexes at a threshold of 69 g and wing chord was nearly diagnostic, whereas range-wide there was greater intrasexual variation and intersexual overlap in both metrics. Locally, females weighed 75.3 ± 5.6 g (range 69.0–94.2 g), and males weighed 62.5 ± 2.5 g (range 58.5–68.5 g); all local males had wing chords