Monterey Bay, California, is a site of regional significance for marine birds. I studied the seasonal abundance of marine birds within 1 km of shore in Monterey Bay during 1999 and 2000. Total bird abundance was greatest during spring and fall migration, whereas diversity was greatest during winter. Species assemblages were fairly consistent by season in both years, but three species were more abundant during summer and fall 2000 than during those seasons in 1999. This increased abundance may have been a response to reduced prey availability outside the study area, related to sea-surface temperature in spring 2000 being higher than in spring 1999. The mean density of all species (363 birds/km²) was considerably greater than the density reported for Monterey Bay as a whole, indicating that the nearshore environment should receive unique consideration in studies of the abundance and distribution of marine birds.