Cassin's auklet uses a few offshore lands for breeding in Oregon. It forages in the marine environment and nests in a chamber under rocks or digs its own burrow, two to six feet long, in the soil. This species spends its day at sea and only comes to the burrow at night, perhaps to reduce discovery by predacious Western gulls.
Although few Cassin's auklets nest in Oregon, nesting sites are found along the entire coast where offshore rocks provide appropriate habitat. During the non-breeding season this is the most abundant alcid seen at sea in Oregon. They are present offshore all year.