White-breasted Nuthatches are common and widespread birds in Oregon, found in mature deciduous and mixed forests, as well as in parks and wooded suburbs. They are known for their distinctive habit of foraging headfirst down tree trunks, a behavior that sets them apart from woodpeckers (which typically climb up).

While both male and female White-breasted Nuthatches share a similar overall appearance, there's a subtle but often reliable difference in their head coloration:
Male White-breasted Nuthatch: The male has a solid black cap that extends from the bill over the crown and nape. This black is typically quite distinct and contrasts sharply with the white face.
Female White-breasted Nuthatch: The female's cap is often dark gray instead of jet black, or a duller black than the male's. While some females can have a fairly dark cap, it generally appears less intense and less defined than the male's.

Both sexes share these common features:
Upperparts: They have a striking blue-gray back.
Underparts: Their face and underparts are bright white, with a rusty or chestnut wash on the lower belly and undertail coverts (the feathers beneath the tail).
Bill: They have a long, sturdy, and slightly upturned bill.
Tail: Their tail is short, with black outer tail feathers that have broad white bands, visible especially in flight.
Behavior: They are active and agile, creeping along tree trunks and large branches, often moving headfirst downwards as they probe for insects and seeds in bark crevices. They are also known to cache seeds.

The distinction in cap color can be subtle and lighting conditions can affect how it appears, so it may not always be immediately obvious in the field. However, it's the primary way to differentiate between the sexes of White-breasted Nuthatches in Oregon.