Current monitoring and management of tricolored blackbirds

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USDA Forest Service, p.169-173 (2005)



Tricolored Blackbirds (Agelaius tricolor) are largely endemic to California. Over 90 percent of the population occurs within the state. Surveys indicate that populations have declined by 37 percent from 1994 to 1997 and by 33 percent from 1997 to 2000. Tricolors are listed as a nongame bird of conservation concern by U.S. Fish and Wildlife Service and a species of special concern by California Department of Fish and Game. Breeding tricolors are colonial, and form the largest colonies of any North American passerine bird. In the 1934 one colony was estimated to have 200,000 nests. Tricolors nest in freshwater wetlands, and upland spiny vegetation such as Himalayan Blackberry (Rubus discolor). They forage away from their nesting habitat. The severe population decline is likely a result of land conversion and heavy nest predation by herons, mammals, and corvids. PRBO Conservation Science and California Partners in Flight have initiated a web-based volunteer program to monitor Tricolored Blackbird breeding colonies. The information collected will be used to estimate tricolor abundance, and form management recommendations. An intensive state-wide census is recommended every three years to calculate population size. Lastly, the project will identify key colonies to manage and enhance. Further research and management recommendations for preserving and creating habitat, are still needed to control the precipitous decline of this

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