Wintering Populations of Lesser Snow Geese and Ross' Geese in the Northern Highlands of Mexico, 1988-1990

To improve delineation of the migration routes and wintering ground affinities of the various Lesser Snow Goose stocks and to clarify the interrelationships of the Wrangel Island, Western Canadian Arctic, and Central Canadian Arctic populations, an international marking-observation program was initiated in 1987. In Mexico, the growing importance of the Northern Highlands as a wintering area for Ross' Geese and the western Central Flyway population of Lesser Snow Geese emphasized the need to conduct field observations in that area. This project estimated the number of Ross' and Lesser Snow Geese on the principal wintering areas in the states of Durango and Chihuahua; determined the breeding ground origin of Lesser Snow Goose stocks overwintering in Mexico by measuring the ratio of marked to unmarked birds, and the ratio of blue to white-phase geese; determined the incidence and number of Ross' Geese among flocks of white geese; and assessed the quality and security of white goose wintering habitat, and identified wetland habitats of critical importance to waterfowl.