These two definitive-basic California
Gulls (Larus californicus) were photographed
by Michael Donahue at Seattle, Washington in Mid-December 1999.
Note the difference in size and mantle tone, plus the thicker
white tertial crescent and slightly longer gap between P8 and
P9 on the paler bird. Update Sept 2000:
Jon King feels that these photos depict the normal variation in
plumage of nominate californicus, rather than a californicus
and an albertaensis: