Territory Establishment, Size, and Tenacity by Male Red-Winged Blackbirds

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Abstract
Most male Red-winged Blackbirds (Agelaius phoeniceus) established their first territories by replacing territory holders that disappeared. These territories were significantly larger than those established either through subdivision of the vacated territory between two or three replacement males, or through insertion of a new territory through displacement of one or more resident males. Almost all returning male Red-wings settled on their former territories in consecutive years. Their territories remained similar in size and location between years. Strong territory tenacity apparently is favored by lower costs of territory defense because of reduced aggression between familiar neighbors and site dominance effects. The lower costs of territory defense presumably also allowed the site-tenacious males to establish larger territories in consecutive years. Strong territory tenacity by returning males could explain much of the settlement pattern of new males. As a result, the spatial arrangement of male territories in the study marsh (i.e. the location of territorial boundaries) was similar in consecutive years. Traditionalism in the male territorial system should influence Red-wing mating patterns.