In winter there are four age and gender classes of the Snowy Owl: first year males, first year females, adult males and adult females. Birds after their second prebasic molt are considered adults. First year females are heavily marked and can be identified in the field with reasonable certainty. Adult males tend to be the least marked and whitest. First year males and adult females are most similar. I aged this Snowy Owl  as a first year male in first basic plumage. Note broken secondary feather. Below are the points used to determine its age and gender.

Photo 1. Extensive mottling of the tertials and greater coverts indicates a first year male. This bird also has mottling on lower scapulars, which adult females do not have. See also Photo 4. Mottling or gray dappling on the tertials and coverts is found in both first year males and females, varying from dark and extensive to slight. Adult females can have slight mottling of the greater primary coverts and distal tips of primaries.

Photo 2. First year males have narrow and less dense ventral bars than females, which have significantly thicker and denser barring. They can have a dark patch of mesoptile down on the hind neck. See also Photos 3 and 5.

Photo 3. On first basic males, the mantle, scapulars, back, upper wing coverts are white with narrow gray-brown crescent-like bars, not as half moon shaped as adult females. The loose feather is a secondary.

Photo 4. Extensive mottling on the tertials, lower scapulars and greater coverts indicates a first year male. Adult females do not have mottling on lower scapulars.

Photo 5. First year males have narrower tail bars than adult females. First basic males have a small patch of mesoptile feathers retained on the hind neck. The loose feather is a secondary.