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DEMOGRAPHY AND REPRODUCTIVE SUCCESS IN THE DUSKY ANTBIRD, A SEDENTARY TROPICAL PASSERINE

Abstract Demographic data are presented from an 8-yr study of a marked population of the Dusky Antbird (Cercomacra tyrannina), a sedentary neotropical passerine with year-long territories and pairbonds. Dusky Antbirds had an annual survival rate of 82%, and the survivorship curve was linear. Sexes did not differ in survival. The probability of reproducing successfully, based on the number of pairs accompanied by independent young the following dry season, was only 8% and no territory produced more than one successful nest, if any. In one year (1997) reproduction was significantly better (25%) than the other years, perhaps associated with lowered predation during an extremely dry wet season. We suggest that for Dusky Antbirds, a species with no extra-pair mating behavior, a long adult lifespan appears to be the primary means to increase lifetime reproductive success.