Active Pass is the water body separating Galiano and Mayne Islands in the southwest portion of the Strait of Georgia. It is about 40 km south of Vancouver and 50 km north of Victoria. It is a tidally active body of water about 4.5 km long. The tidal mixing during the floods and ebbs creates a biologically rich feeding area for fish eating birds, mostly during the spring, fall and winter. In addition to birds, orcas feed and travel regularly through the pass from spring to fall, while Dall’s and harbour porpoise and Steller’s sealions are occasional visitors. The pass is also known for a rich intertidal and subtidal fauna.

Active Pass supports nationally, continentally or globally significant populations of Pacific Loon and Brandt's Cormorant (in winter), and Bonaparte's Gull (on migration). The 2,000 Pacific Loons that regularly occur at the pass during winter comprise the largest concentration in the Strait of Georgia. In addition, about 4,000 wintering Brandt's Cormorants have been recorded here. Bonaparte's Gulls pass through in large numbers, with about 10,000 recorded during fall migration, and daily maximum counts of between 7,000 and 15,000 birds recorded during spring migration. The continental or global significance of these counts may require re-evaluation against the most recent estimates. Several pairs of Bald Eagles nest along the shores of the pass, and upwards of 100 eagles occasionally forage in the waters during the winter.

The significance of Active Pass is linked to the rich feeding area that is created by the ebb and flow of the tide through the channel. Threats to the birds utilizing this area are limited primarily to potential oil spills or oil discharges from ships, and possibly excessive disturbance from recreational and ferry boats. Pacific Loons are especially vulnerable during their winter flightless period when they undergo wing moult. The pass is well known to bird watchers because of the accessibility afforded by the hourly passage of ferries between Vancouver and Victoria.