Gillam Islands lie about 2 km off the mainland shore of Vancouver Islands Quatsino Sound. The islands have rocky shores (steep in some areas), with numerous small crevices and gorges. The larger northernmost island is forested, with Sitka Spruce being the dominant species. Below this canopy, thick growths of salmonberry and currant form most of the understorey, along with patches of salal, elderberry, and crabapple. On the other islands, dwarfed spruce is present, along with shrubby thickets that are comprised of the same understorey vegetation as on the northernmost island. Lush grasses and forbes crown the middle island and surround the perimeters of the northern and southern islands. The other low rocky islets in the group are devoid of vegetation.
Gillam Islands support the second largest storm-petrel colony in British Columbia, with both Fork-tailed and Leachs Storm-Petrels being present. Together with Solander Island to the south, and the Storm Islands to the northeast of Vancouver Island, these three island groups contain the majority of the storm-petrel nesting population on Canadas west coast. On Gillam Islands, surveys completed in 1988 documented the presence of a globally significant Fork-tailed Storm-Petrel colony with 42,000 nesting pairs being present (1.7% of the global and about 22% of the national population). A globally significant Leachs Storm-Petrel colony was also documented during the same survey with 72,000 pairs being recorded (2.6% of the global and 13% of the national eastern Pacific population).
In addition to the storm-petrels, just over 1% of Canadas Black Oystercatcher population nest on these islands, along with about 2.6% of the Canadas Glaucous-winged Gull population. Other seabirds that nest on the islands include smaller numbers of Pelagic Cormorants, Pigeon Guillemots, and possibly Tufted Puffins.
Conservation responses/actions for key biodiversity
Primary threats to the Gillam Islands are potential oil spills and the possibility of disturbance from boaters. Since the islet chain is within the mouth of Quatsino Sound, it has calmer waters which make it an attractive destination for recreational boaters.