California Gulls are birds of inland plains while breeding and are found on sea coasts in winter. In Canada, they breed from southern Mackenzie District south through eastern Alberta and Saskatchewan to southwestern Manitoba and in interior southern British Columbia. The winter distribution extends along the Pacific coast of North America from southern British Columbia south to Mexico (Winkler 1996). Small numbers winter inland in the lower Colorado River area, in Texas, and in the Salton Sea of southern California. This gull is common in southern British Columbia coastal waters in fall and spring, occurring as far north as the Queen Charlotte Islands (Campbell et al. 1990b).
Encounters (including sight records) of chicks banded in Saskatchewan were analyzed by Houston (1977), and encounters of birds banded in Alberta were analyzed by Vermeer (1970a); their results are treated here as representative of the Canadian population. Both studies found a striking pattern of westward movement to the Pacific coast in the fall; in some cases, birds reached the coast within 6 weeks of banding (record 1). In September and October, birds from the Canadian Prairies share the refuse dumps and shores of southern British Columbia with others that have moved north and west from breeding grounds in the United States; most birds then move south for the winter. Virtually all Canadian-banded first-year birds, and about half the second-year birds, remain on the coast for the following summer, when older birds return to their prairie breeding grounds.
Canadian-banded birds have been encountered in Mexico (19: Baja California, 12 [record 2]; Sonora, 5 [record 3]; Sinaloa, 2 [record 4]), California (51 [record 5]), North Dakota (2), Texas (2), Kansas (1), Oregon (8), and Washington (13). The farthest movement was from Alberta to the Gulf coast of Louisiana (record 11). One bird banded in Alberta was encountered as an adult 8 years later, in Minnesota in June (record 6), demonstrating that not all young birds return close to their natal area.
Large-scale banding at colonies in the northwestern United States has resulted in numerous encounters in British Columbia, mostly in the Vancouver area. These birds originated from California, Oregon, North Dakota, Wyoming, Utah, Montana, and Idaho. The great majority of these encounters involved birds whose band numbers had been read by telescope. This technique, while very welcome, introduces a further bias into the recovery pattern; the chance of encounters is influenced, as always, not only by the density of human population, but also by the presence of people willing to sit down with a telescope observing gulls' legs. There are, for example, no fewer than 56 encounters in Burrard Inlet and adjacent Beach Grove, British Columbia, of birds banded as locals at Freezeout Lake, Montana (record 7). A substantial number of encounters are multiple — i.e., several observations of the same bird, frequently in subsequent years (record 8).
Origins of birds banded as locals and encountered (excluding multiple encounters) in the Lower Mainland of British Columbia were as follows: Colorado, 1; Nevada, 1; North Dakota, 9 (record 9); Montana, 169; Utah, 15 (record 10); Idaho, 46; Wyoming, 93; California, 18; Oregon, 11; Washington, 55. Banding locations in the last three states were inland. In agreement with the Canadian experience, the great majority of encounters were in the first and second years of the birds' lives. Inland encounters were as follows: Montana to Saskatchewan, 4; Montana to Alberta, 2; and Wyoming to Saskatchewan, 4. As with Canadian records, several of these encounters involved birds of breeding age.
Two encounters in Louisiana (record 11) occurred before the species had been recorded in that state; their occurrence was not confirmed until fall of 1985 (J.V. Remsen, pers. commun.). Unfortunately, these band recoveries, and perhaps the one in Minnesota, must be treated with the greatest reservation because California Gulls are very similar to Ring-billed Gulls (which are abundant in Louisiana in winter) and breed in mixed colonies on the prairies; their chicks are virtually indistinguishable in the field (Salt and Salt 1976). Ring-billed Gulls had been banded at the same locality as these "California" Gulls, although not in the same year. There must, therefore, always be some doubt that birds banded as chicks were identified correctly.
The oldest encounter of a bird banded in Canada was of a nestling banded at Great Slave Lake, Northwest Territories, and encountered in the same area nearly 13 years later (record 12). The oldest bird banded in the United States and encountered in Canada was 11 years old when reported (record 13). Only one other encounter exceeded 10 years — a remarkably low apparent survival for a gull (cf. Ring-billed Gull,Herring Gull).