Territoriality, Adult Survival, and Dispersal in the Checker-Throated Antwren in Panama

A marked population of Checker-throated Antwrens Myrmotherula fulviventris was studied on Barro Colorado Island, Panama over a 14-year period. Once established on territories, Checker-throated Antwrens were found to be relatively long-lived both males and females, which survive at least one year, live an average of four years; annual survival of territorial adults was 75%. After the first year, survivorship declined as birds aged; younger birds had a survivorship of 85-90 % and older birds survived at an average of 50-76%. Territory boundaries were generally stable throughout the period despite substantial turn-over of individuals. Although territories are a stable and indivisible feature of the habitat, 37% of the marked adults shifted to neighboring territories at least once in their life. The frequency of switching appeared to be independent of sex or age. A large portion (59%) of the fledglings dispersed to within two territories of where they were hatched. Opportunity to improve territory quality appears to be largely limited to short-distance dispersal in both sexes of this species. Limited options for improving territory quality may explain the intense and often lengthy territorial boundary displays which occur on a daily basis. The need to provide defense against the intense competition for limited reproductive slots in the population may also explain the declining survivorship in territorial adults.