My little project within Allyson’s enormous project is looking at primary feathers of thrushes (and hopefully other families next term) and their Hg levels. The question that I would ideally be able to answer by the end is whether total Hg in adult primary feathers is dependent on their molt pattern in the American Robin, Varied Thrush, Hermit Thrush, and Swainson's Thrush. One challenge I have discovered in my literature search is the lack of dependability on feathers as an Hg indicator. This is one of the main reasons I chose to do this project, to see if certain feathers can be more reliable or give us more information than others. There is some discrepancy over the correct unit to use when trying to quantify mercury in a feather. Most research utilizes ppm of Hg as their measurement, but one paper, Bortolotti 2010, claims that using a unit of Hg mass (ng)/feather length (mm) is the appropriate unit since Hg is deposited in the feather according to abundance of Hg in blood at the time of growth. I’m hoping that the results I get from this term and next term will begin to shed some light on which unit makes sense to use for mercury and why.
To do this, I measured feather length and prepped the left and right primaries for these species (12 birds total) to get run through the lab’s mercury analyzer. I currently have the data from the left primaries for the thrushes and am attempting to form my next steps in this project.
Both graphs show the quantity of Hg in each primary feather (average of all 12 birds). The first graph is in ppm Hg while the second is in Hg (ng)/feather length (mm). They both show the same pattern with increasing primary feather number. This may indicate that either unit may be appropriate to quantify Hg levels in feathers.