Demographic comparison of Golden-Winged Warbler ( Vermivora chrysoptera ) populations in northern and southern extremes of their breeding range

Conservation strategies for declining species often are based on limited knowledge about how fecundity and survival may change across a species' range, and what factors may be limiting for a given population. Incomplete understanding of how a species' demography varies across a range of conditions may lead to inappropriate management decisions. Our objective was to compare demographic data from northern and southern extremes of the breeding range of Golden-winged Warblers (Vermivora chrysoptera). Specifically, we compared minimum estimates of annual adult survival, daily nest survival, fecundity, and population growth (lambda) for Tennessee and Ontario breeding populations. Tennessee nest survival decreased throughout the nesting season and as daily minimum temperature increased, but the constant survival model was equally supported (model averaged daily survival rate, DSR = 0.972 [0.01 SE]). Ontario nest survival also decreased throughout the nesting season, but not as a function of temperature (model averaged DSR = 0.956 [0.02 SE]). Despite larger clutch sizes and number of young fledged per successful nest in Ontario, fecundity estimates were greater for the Tennessee population. Males had greater annual survival than females in both Tennessee and Ontario populations (Tennessee male = 0.616 [0.11 SE], Tennessee female = 0.427 [0.12 SE], Ontario male = 0.618 [0.08 SE], and Ontario female = 0.477 [0.14 SE]). Minimum lambda estimates suggest that both populations were declining (λ = 0.7468 and 0.7935 for Tennessee and Ontario, respectively). However, as with many mark-recapture studies of birds, we are unable to separate mortality from dispersal which likely biases these survival estimates. Further, annual survival is affected by events in the wintering and migratory periods and until these are known, we will be limited in our ability to effectively manage this and other declining Neotropical migratory songbirds.