Steller's Jays are common and striking birds found throughout Oregon, particularly in forested areas, parks, and even suburban backyards. When it comes to telling males and females apart, it's generally quite difficult based on appearance alone. This is because Steller's Jays are considered to be monomorphic, meaning both sexes look very similar.

General Appearance (Both Sexes):
Size and Shape: They are medium-sized, robust jays, larger than a robin but smaller than a crow. They have a prominent, shaggy crest on their head, a strong, pointed bill, and a relatively long tail.
Coloration: Their plumage is a striking combination of deep black and vivid blue.
Head and Crest: The head, crest, and upper back are typically black or very dark charcoal gray.
Body and Wings: This dark color fades into a bright, rich blue on the lower back, wings, and tail. The wings and tail often have subtle black barring.
Forehead/Eyebrow (subspecies variation): Some subspecies, particularly those found inland or in the Rockies, might have small white or pale blue spots on the forehead or near the eye. Coastal populations tend to have darker heads with less or no white marking. Oregon has both coastal and interior forms, so you might see slight variations.
Vocalizations: Steller's Jays are known for their wide range of loud, harsh, and sometimes mimicry calls. They are highly vocal birds.

Subtle Differences and Behavioral Cues (where distinctions might be observed):
While visually very similar, there are a few subtle differences and behavioral cues that might help distinguish between males and females, especially during the breeding season:
Size (minimal): Males are very, very slightly larger on average than females, but this difference is so marginal it's virtually impossible for a casual observer to use for identification.
Tail Barring (subtle): Some sources suggest that females might have slightly fainter and narrower black barring on their tails, but this is not a consistent or reliable distinguishing feature.
Bill Length (scientific measurement): In some subspecies, researchers have found a very slight difference in culmen (upper bill) length, where males might have a slightly longer bill. However, this requires precise measurement and is not useful for field identification.
Behavior during Breeding Season: This is where you're most likely to see behavioral differences:
Courtship Feeding: During courtship, the male Steller's Jay will often feed the female. If you observe a jay repeatedly bringing food to another, it's highly likely the feeder is a male and the recipient is a female.
Nest Building: While both sexes participate in selecting the nest site and gathering materials, the female generally takes on the majority of the actual nest construction.
Incubation: The female primarily incubates the eggs (typically 2-6, pale blue-green with brown spots) for about 16-18 days. During this time, the male will often bring food to the incubating female.
Parental Care: Both parents feed and care for the nestlings once they hatch.
Vocalizations (subtle differences): While both sexes are noisy, males may sing more regularly and directly. Some specific calls might be gender-specific. For example, females are said to have a distinctive "mechanical rattle" call that males generally don't make, while males might have a "creaking whistle" call. These subtle differences can be hard to pick up unless you're very familiar with their vocalizations.