On the east coast of Vancouver Island in winter, one of the most common gulls encountered is the Mew Gull (Larus canus). Mew Gulls can be found roosting or feeding in most marine shoreline habitats in winter, as well as further offshore when food is plentiful. Although they can be found up rivers when salmon are spawning, it is far more typical to find them in marine areas in the non-breeding season. By early May, virtually all Mew Gulls leave the Salish Sea, and move to freshwater areas to nest. Some will migrate far into the boreal forest or even into the low Arctic to nest, while others will only travel a short distance to nest on freshwater lakes on Vancouver Island. I have found them nesting on lakes near sea level, all the way up into the high alpine. It has become rare to find them nesting on any lake frequented by humans though.
By July, Mew Gulls begin returning to the Salish Sea, and by October, winter numbers are again present. The greatest numbers occur on the east coast of Vancouver Island during the Pacific Herring Spawn in early spring. Counts of over 20,000 Mew Gulls at one site do occur at the height of spawning activity.
Mew Gulls generally nest on the ground, but will also build nests on pilings, broken snags, and in abandoned nests of other species well above the ground in trees. Nests are usually built of sticks, roots and mosses. Occasionally, eggs will simply be laid on existing moss with no materials added. They lay from one to five eggs, with three being average. Eggs are brooded for about 25 days and it generally takes about 30 days for young to fledge. Mew Gulls can nest singly, or in colonies.