U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version

November 2003


Red-winged blackbirds (Agelauis phoeniceus) have a polygynous breeding system that results in a group of nonbreeding males (floaters) who are unable to obtain territories. Floaters are often unaccounted for in population estimates during the breeding season because they are difficult to locate. We used a series of removals to estimate the population of non-breeding after-second-year male red-winged blackbirds in two townships in the northern Great Plains. The number of floaters determines the level of competition for vacant territories. In our study population, we estimated there were more floaters than territorial males, indicating that competition for vacant territories was strong. Finally, we failed to detect any evidence that our removal efforts reduced the number of floaters in the subsequent years.