Mercury (Hg) is a bioaccumulative metal that can threaten the health of wild birds. Feathers are commonly used biomonitoring tools for non-lethally estimating Hg exposure in birds because they contain stable Hg concentrations upon completion of feather growth, when blood flow to the feather has stopped. Despite the common use of feathers as indicators of avian exposure, little is known about how feather concentrations relate to internal tissue exposures. Songbird feather physiology and how factors such as molt may impact Hg sequestration into songbird feathers are particularly lacking. To understand sequestration of Hg into primary feathers, we examined patterns of Hg concentrations among the 9 primary feathers of individual birds where molt order was known. Hg concentrations in the left primary feathers from 30 salvaged individual specimens from families Turdidae and Passeridae (Catharus ustulatus, Ixoreus naevius, Turdus migratorius, Melospiza melodia, Zonotrichia atricapilla, Passerella iliaca, Pipilo maculatus, Junco hyemalis) were measured. Preliminary results indicated that a conclusive trend in Hg concentration with increasing primary feather number was lacking, with only small variation in Hg concentration among primary feathers. A mixed effects repeated measures test yielded a p value of 0.2700 with ppm as the fixed effect and bird i.d. as a random effect. Similar studies in seabird primaries have shown strong downward trends in Hg ppm with molt order. The lack of a trend in songbird primaries may be influenced by diet shifts during molt or changes in sequestration to other feather tracts and body tissues. Conclusions on Hg exposure in birds based on feathers must take time and location between feather growth and the feather sampling into consideration
