Territory switching behavior in a sedentary tropical passerine, the dusky antbird (Cercomacra tyrannina)

Demographic data from an 8-year study of a marked population showed that switching territories and mates is common in both genders of dusky antbirds (Cercomacra tyrannina), a sedentary neotropical passerine with year-round territories and pairbonds. We conducted 22 experimental removals and followed six natural disappearances to examine territory switching. Antbirds quickly abandoned territories and mates to move to openings created by experimental removals. Pairing with the resident on a new territory was rapid. Unmated birds attracted new mates by singing a gender-specific song that differed from songs given by mated birds. There were no gender differences in replacement time or rate. Some vacancies, experimental and natural, were not filled, suggesting that floaters were rare. Territory and mate switching were not related to immediate enhancement of reproductive success because the probability of reproducing successfully was equally poor on all territories. Territory switching may be an overlooked but common tropical form of territoriality that increases individual survivorship during periods of low food abundance (dry season). We suggest that switching is favored when low annual reproductive success enhances selection for a long lifespan as the primary means to increase reproductive success.