Rankine Islands and Langtry Island lie off the mouth of Carpenter Bay near the south end of Moresby Island. Included in the IBA are the marine waters within a five km radius of the islands. Most of the vegetated areas of the larger west Rankine Island are forested with Sitka Spruce, Western Red Cedar, and Western Hemlock being dominant species. Where windfalls have occurred, areas of young re-generating spruce predominate. The smaller eastern islet has extensive bare rocky areas around the shore, with lush grass and forbs under a sparse stand of spruce that grades into thicker forest habitats. Langtry, the other island supporting nesting seabirds within this area, has a luxuriant cover of herbaceous vegetation and deciduous shrubs under an open spruce forest.

Although small in size, the islands within this site support dense breeding colonies of four seabird species: Ancient Murrelets, Cassins Auklets, Fork-tailed Storm-Petrels, and Leachs Storm-Petrels. All four species occur on Rankine Islands, while Langtry supports only Fork-tailed and Leach?s Storm-Petrels.The colony of Ancient Murrelets on west Rankine Island is the third largest colony in British Columbia. In the mid-1980s, a population of about 26,200 pairs was estimated, which represents about 5.2% of the global and nearly 10% of the national population of this species. Cassin?s Auklets are also present in globally significant numbers with about 25,800 pairs being estimated on the Rankine Islands (about 1.4% of the world?s population). Nationally significant populations of Fork-tailed Storm-Petrels (at least 1%) and Leach?s Storm-Petrel (greater than 2% of the eastern Pacific population) are also present among the islands.

Other seabirds nesting on the islands include Pigeon Guillemots and Glaucous-winged Gulls. Black Oystercatchers are also present with as many as 8 pairs being estimated in the mid-1980s. The marine waters surrounding the island colonies provide important feeding habitat for marine birds. Bald Eagles nest on each of the islands and Peregrine Falcons (ssp. pealei) are recorded in the area.

Rankine and Langtry Islands are located within the Gwaii Haanas National Park Reserve. Prior to the formation of this reserve, Rankine Islands were designated as a British Columbia Provincial Ecological Reserve (since 1973). The primary threats to the area are from potential oil spills, and possible disturbance from boaters and other visitors. The seabird colonies are fragile, particularly the storm-petrel colonies on Langtry and east Rankine Island. The spread of introduced predators (mainly raccoons, which are found on nearby Moresby Island, is also a potential threat.