Chronic low reproductive success of the colonial tricolored blackbird from 2006 to 2011

Abstract

I studied the Tricolored Blackbird (Agelaius tricolor) in California's Central Valley over six breeding seasons from 2006 through 2011 and documented fates of nesting attempts, reproductive success of colonies, and relative abundance of insect prey in foraging areas. I found widespread and chronic reproductive failures except in cases of relatively high insect abundance. My observations suggest that the productivity of Tricolored Blackbird colonies is food-limited and that the relatively high reproductive success at few colonies is primarily a function of unusually high abundance of insects in nearby foraging areas.