Late nesting Tricolored Blackbirds in western Marin County, California

Abstract

Since my earliest actual surveys of Tricolored Blackbirds (Agelaius tricolor) on outermost Point Reyes in 1982, the winter population has ranged from 4,500 to 11,000 individuals. In most years the number has been in the 9,000 to 11,000 range, perhaps 8-10% of the world population. Winter birds forage at dairy ranches on the outer point and roost in freshwater cattail (Typhus spp.) marshes and introduced Monterey Cypress (Cupressus macrocarpa) groves. Numbers begin to dwindle by late February and by early April the species is virtually absent. There are none present for most of April and May.