Avian mercury concentration can be measured using feathers, which are easily collected and analyzed. Feather collection has resulted in archives of samples spanning decades. Mercury concentrations (henceforth [Hg]) in breast tissue is of interest; it is most often consumed by hunters and is less variable than feathers, so may better represent the effect of mercury on avian survival and reproduction. The relationship between feather and breast [Hg] is relatively unknown. Understanding this relationship may permit using feathers to predict breast [Hg]. We collected 39 wood ducks harvested by hunters on the Carson River, NV, an area highly contaminated with mercury. We measured [Hg] in axillary and flank feathers and liver and breast tissue using a Milestone DMA-80 mercury analyzer. We examined the relationship between these tissues using a multivariate log-normal regression model within a Bayesian framework. We found a positive correlation between flank feathers (Beta = 0.82; 95% CRI = 0.64—0.99) and breast [Hg], although there was considerable variability. We developed a predictive tool to estimate the 95% credible interval of breast [Hg] using flank feathers, permitting us to use flank feathers to determine if hunter consumption advisories are warranted and estimate historical breast [Hg] from archived feather samples.