Purple Martins are the largest swallows in North America, and their appearance differs significantly between males and females, particularly with age. In Oregon, where their populations are often more reliant on natural cavities than the human-provided houses common in the East, knowing these differences is key to identification.

General Appearance (Both Sexes):
Size and Shape: Large, broad-chested swallows, measuring around 7.5-8.5 inches (19-22 cm) in length, with long, tapered wings and a short, slightly forked tail. They have stout, slightly hooked bills.
Flight: Powerful and graceful fliers, often soaring and gliding high in the sky as they hunt large aerial insects like dragonflies. They have a characteristic deep, rich gurgling call.
Habitat: In Oregon, they are often found in open woodlands, particularly near water bodies like lakes, rivers, and coastal estuaries. Unlike their eastern counterparts, western Purple Martins are less dependent on human-provided nest boxes and more commonly nest in natural tree cavities (especially old woodpecker holes) or crevices in human-made structures like pilings.

Male Purple Martins:
Adult Males (After Second Year - ASY): These are the most distinctive. They are entirely glossy, iridescent bluish-purple all over, including their underparts. In poor light, they can appear almost black, but in good sunlight, the rich purple sheen is unmistakable. This solid dark coloration makes them unique among North American swallows.
First-Year Males (Second Year - SY): This is where it gets a bit trickier, as Purple Martins exhibit "delayed plumage maturation." First-year males resemble females (see below) but often have blotchy or scattered patches of iridescent purple-black feathers on their chest, belly, and sometimes throat or head. The amount and location of these dark patches can vary greatly.

Female Purple Martins:
Adult Females (After Second Year - ASY): Adult females are duller than adult males. They have dark, iridescent bluish-purple or brownish-blue upperparts (back, head, wings), similar to the male, but their underparts are grayish, transitioning to a paler or dingy whitish on the lower belly. They often have a grayish collar around the neck and a paler forehead. Some older females can show more blue iridescence on their backs.
First-Year Females (Second Year - SY): Younger females are even duller and browner overall, especially on the back and head. Their underparts are typically a more uniform grayish or dirty white, with less defined patterns than older females. They lack the dark blotches seen on first-year males.

Key Differences to Look For (especially in Oregon):
Overall Coloration: The adult male's solid, glossy blue-purple plumage is the most obvious distinguishing feature. If you see an all-dark swallow with a slightly forked tail, it's a male Purple Martin.
Underparts: This is crucial for distinguishing females and first-year males from other swallows and from adult males. Females and first-year males will have varying degrees of gray or white on their underparts, never entirely dark like an adult male.
Chest and Belly Patches: If you see a largely gray/white-bellied bird with sporadic, splotchy dark purple feathers on the chest or belly, it's likely a first-year male transitioning to adult plumage. Females will lack these dark patches.
Facial Markings: Unlike Violet-green Swallows with their prominent white cheek patches, Purple Martins lack distinct white facial markings.