California Scrub-Jays are ubiquitous and charismatic birds throughout much of Oregon, particularly in the western valleys, foothills, and urban/suburban areas with oak trees and dense shrubs. Unlike many bird species where males and females have distinct plumage, California Scrub-Jays are monomorphic, meaning that male and female birds look remarkably similar in appearance.

General Appearance (Both Sexes):
Size and Shape: They are medium-sized songbirds, slightly larger than an American Robin, with a sturdy build, a relatively long tail, and a stout, straight bill with a slightly hooked tip. They **lack a head crest**, which immediately distinguishes them from Steller's Jays.
Coloration: They have a distinctive and attractive color pattern:
Head, Wings, and Tail: Bright, rich azure blue. This can appear more purplish or duller depending on the light.
Back: A patch of grayish-brown on the upper back, which contrasts with the blue head.
Underparts: A clean, pale gray to white belly.
Throat and Chest: White throat bordered by a partial blue-gray "necklace" or breast band.
Face: They have a white "eyebrow" (supercilium) and a dark cheek patch, often appearing blackish around the eye.
Bill, Legs, and Feet: All are black.
Vocalizations: They are known for a wide variety of harsh, scratchy, and sometimes musical calls. They are very vocal birds.

Subtle Differences and Behavioral Cues (where distinctions might be observed):
Since visual differentiation is so hard, observing their behavior, particularly during the breeding season (roughly March through July in Oregon), is the most reliable way to infer sex.

Size (Minimal): While not discernible in the field, scientific measurements show that males are, on average, very slightly larger than females in terms of body mass and some linear measurements (like bill length). This difference is too small to be used for identification by eye.
Behavior during Breeding Season:
Pair Bonds: California Scrub-Jays form strong, monogamous pair bonds and often stay together year-round, defending their territory.
Courtship Feeding: During courtship and incubation, the male will often feed the female. If you observe one bird repeatedly bringing food to another, the feeder is likely the male and the recipient is the female.
Nest Building: Both sexes participate in choosing the nest site and gathering materials. However, the female typically does most of the actual nest construction. Nests are cup-shaped, well-built structures of twigs and grass, often lined with rootlets or animal hair, usually located in a shrub or low tree (5-15 feet off the ground).
Incubation: The female does all or almost all of the incubation of the 2-7 eggs (typically 3-5), which are usually light green with brown spots. The incubation period is about 17-18 days. During this time, the male will bring food to the incubating female.
Parental Care: Once the nestlings hatch, both parents feed them. Young fledge (leave the nest) after about 18-22 days but remain dependent on their parents for at least another month.
Territorial Defense: Both sexes are highly territorial year-round, but males may be particularly aggressive in defending their breeding territory.

Juvenile California Scrub-Jays:
Young California Scrub-Jays look similar to adults but have duller, less vibrant blue plumage, often with a brownish wash. Their facial markings might be less distinct, and their bills can sometimes appear paler. They gradually acquire adult coloration as they mature.