Each year, monarchs congregate in colonies along the California coasts. Although not as well-known as the colonies in Mexico, the overwintering grounds of the western population are also critical for their survival and monitored each year by volunteers for the Xerces Society. The "Thanksgiving" Counts are performed each year in the fall after monarchs have returned from their breeding grounds. Although 450 sites have been documented as having supported monarchs at some time, under 300 sites are regularly counted. The main colonies are monitored every fall and other colonies less frequently. This program keeps track of the overwinter populations. Formerly known as the Thanksgiving Monarch Counts, this program has expanded to include New Years counts and is now part of the Western Monarch Count Resource Center.