Honors College Thesis

 

Songbird feathers as indicators of mercury exposure : Patterns across feather tracts and correlations to other tissues Public Deposited

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https://ir.library.oregonstate.edu/concern/honors_college_theses/pk02cc522

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  • Monitoring mercury (Hg) exposure in avian populations is critical to understanding the effects of this neurotoxin. Avian Hg exposure is commonly evaluated by measuring Hg concentrations in internal tissues, blood, and feathers. Feathers are a popular sampling matrix due to ease of sampling and limited stress to birds. However, it remains unclear if feather Hg is representative of the Hg load in the body, which is more relevant to toxicological evaluations. Furthermore, it is unclear which feathers should be sampled, given that Hg sequestration patterns across feather tracts are poorly understood. To better understand these patterns, we tested variation in Hg concentration across five feather tracts (crown, left breast, belly, back, left flank) in 37 salvaged songbird specimens in the Thrush (N=22) and Sparrow (N=15) families. We then compared feather Hg concentrations to those of internal tissues in the same birds, to test the relationship between feather and body Hg load. Our results indicate no statistical difference in Hg concentrations across feather tracts, but a high degree of intra-individual variability. Results also suggest a high correlation between liver and muscle Hg concentrations, but weak Hg correlations between internal tissues and feathers. Based on these results, we concluded that feathers from any of the five tracts would yield similar estimates of Hg exposure, however we recommend using a composite of various body feathers. Hg sequestration into feathers may be influenced by factors such as species and feather size, although further research into the effects of these factors is needed. Weak relationships between feather Hg and internal tissue Hg suggest that feather sampling may not be reliable for monitoring fine-scale trends of Hg exposure in songbirds. However, we show a stronger Hg correlation among internal tissues and another keratinaceous structure – toe nails which, unlike feathers, grow continuously. Further investigation into the viability of toe nails as a Hg sampling method is needed.
  • Key Words: mercury, songbirds, feathers, nails
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