Great Slave Lake in the Northwest Territories is one of the most important areas for inland breeding gulls and terns (larids) in northern Canada. Numerous rocky islands on the North Arm provide breeding habitat for a number of colonially-nesting larid species. This report summarizes data and information on active larid breeding colonies collected between 1986 and 2010 on the portion of the North Arm west of Yellowknife. Most data were collected through ground surveys, with travel by boat, between mid June to early July. Information recorded at each colony included species, numbers of nests, clutch size, presence of chicks, and habitat characteristics (vegetation cover). A series of maps displaying the distribution and density (shown as nests/km2) of larid colonies on the North Arm was created for each species and year of surveys. Within Great Slave Lake, the section of the North Arm west of Yellowknife was of particular importance to Ring-billed Gull, Common Tern, Caspian Tern, and to a lesser extent Herring Gull and Arctic Tern. Great Slave Lake as a whole may support nationally significant
numbers (>1% of the national breeding population) of five larid species: Herring Gull (>2,800 adults, 1.7%), Mew Gull (>900 adults, 0.8% - 1.9%), California Gull (>5,000 adults, 2.4% -4.0%), Common Tern (>1,800 adults, 1%), and Caspian Tern (>470 adults, 1.4% - 2.4%).