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Chain Islets & Great Chain Island (BC045)


Chain Islets & Great Chain Island (BC045)

Victoria, British Columbia

Latitude 48.420°N
Longitude 123.269°W
Altitude 0 - 5m
Area 1.38km²

Site Description

The Chain Islets and Great Chain Island are located in Oak Bay, in the Strait of Juan de Fuca, less than 2 km from the suburbs of Victoria, British Columbia. The site includes a cluster of at least 18 small islets and rocks in Mayor Channel. The low round islets are rocky and barren except for Great Chain Island that supports a nearly continuous grass and herbaceous cover and occasional shrub thickets. Shoreline features include a few steep faces, rocky outcroppings, boulders, crevices and small gravel beaches. The islets are surrounded by shallow water from which many rocky reefs emerge. The site includes the marine waters within a radius of approximately 700 m. A large population of Harbour Seals occur year-round.


Significant Species - Chain Islets and Great Chain Island IBA is a site of global importance, supporting a significant breeding population of Glaucous-winged Gulls, and a migratory population of Brandt's Cormorants. Surveys in 1986 recorded 2,432 pairs of Glaucous-winged Gulls breeding on the islands. At that time, the colony of Glaucous-winged Gulls was the largest in British Columbia and, together with two other similar sized colonies in the strait (Mandarte and Mitlenatch), supported 25% of the breeding Glaucous-winged Gulls in British Columbia. A survey in 2009 recorded 1410 nesting pairs on the islands and this site continues to host a breeding population of Glaucous-winged Gulls.

In fall, up to 2,000 Brandt's Cormorants have been recorded in the area. A Pelagic Cormorant colony was also present at this site. In 1987, the population peaked at 248 pairs, but since that time has steadily declined and no Pelagic Cormorants have been recorded nesting here since 2007.

Double-crested Cormorants, which in British Columbia nest only in the Strait of Georgia, were recorded nesting in these islets. The population peaked at 686 pairs in 1990, and this was the second largest colony of this species in the province. The population steadily declined and no Double-crested Cormorants have nested here since 2007. All three species of cormorants continue to use the IBA area through the year. Glaucous-winged Gulls do continue to nest and the habitat remains intact.

Other Species of Conservation Interest - Pigeon Guillemots and Black Oystercatchers also nest on the islets. Harlequin Ducks are present all year. Shorebirds and waterfowl use the protected waters, islets and rocky reefs during migration.

Conservation Issues

The site is part of the British Columbia Provincial Ecological Reserve # 94, Oak Bay Island, with access restricted. Permission to land is required. Despite this designation, the proximity to Victoria has led to some disturbance from boaters who land to picnic and party on the islands. The breeding seabirds are susceptible to disturbance and the local plant communities are sensitive to damage from trampling. These islands and the wildlife they support are vulnerable to disturbance from increased tanker traffic and the possibility of an oil spill.

IBA Criteria Habitats Land Uses Potential or Ongoing Threats Conservation Status
Heermann's Gull
Number Year Season
30 - 602021Fall
110 - 1302015Fall
Brandt's Cormorant
Number Year Season
Glaucous-winged Gull
Number Year Season