Sidney Channel is a 4 km wide body of water that lies along the extreme southeast shore of Vancouver Island between James Island (and the larger Saanich Peninsula) and Sidney Island. Along with Haro Strait, it connects the Juan de Fuca and Georgia Straits. Both Sidney and James Island are overlain by unconsolidated glacio-marine and outwast sand deposits. Large schools of a smelt, known as sandlance, reproduce in the sand, and subsequently attract large flocks of seabirds in spring and summer. The eroded sand has also formed a lagoon at the northwestern end of Sidney Island, which attracts hundreds of sandpipers in the spring and summer.
Sidney Channel is noted for the variety of marine birds that occur at the site throughout the year. Although most places along the south coast of the Strait of Georgia have relatively few birds in summer, the channel and lagoon on Sidney Island are well known for the presence of murrelets, auklets, cormorants, gulls and shorebirds. During winter, seaducks are spread throughout the channel, and during the spring they are joined by migrating grebes, loons, brant, and shorebirds.
Of particular significance at this site are the large concentrations of Brandts Cormorants during fall migration (just over 1% of the worlds estimated population), and Mew Gulls and Brant during spring migration (about 1% of the northeastern Pacific Mew Gull population, and 1-2% of estimated Pacific Brant population). During fall, winter, and spring, large number of Pigeon Guillemots are also present (almost 3% of the estimated national population) and about 300 Brant over-wintered in 1996-1997. In addition, about 20 pairs of nesting Black Oystercatchers (about 2% of the estimated national population) nest on islets located in the area.
About 50 Marbled Murrelets (listed as nationally threatened) are also regularly reported at this site. Although breeding sites for these birds have not been found, these observations may represent a remnant local breeding population. (Many of the southern Georgia Strait breeding populations have been extirpated as result of the cutting of old growth forest). In addition to the Marbled Murrelets, about 50 Great Blue Herons (ssp. fannini nationally vulnerable) are also regularly recorded feeding at this site. In 1988, 100 pairs were reported to nest on Sidney Island, but since then the colony has been abandoned.
BirdLife International (2020) Important Bird Areas factsheet: Sidney Channel. Downloaded from http://www.birdlife.org on 03/12/2020.