Effects of mercury contamination on individual quality and condition of Common Yellowthroats (Geothlypis trichas)

Historic mines in New Almaden, CA such as the New Almaden Quicksilver Mine (NAQM), are a source of mercury contamination throughout South San Francisco Bay, California. Mines in this area drain into the Coyote Creek (CC) and Guadalupe River (GR). Water quality and sediment assessments for mercury show increasing levels with increasing proximity to the New Almaden. Tellingly, birds captured at upper GR and CC had some of the highest reported concentrations of mercury in the feathers and blood within the United States. Thus, organisms living within the riparian habitats along the CC, GR, and their tributaries may be affected by local environmental mercury. This study investigates of the feather mercury from Common Yellowthroats (Geothlypis trichas) caught at varying distances from NAQM and the relationship between feather mercury and of body condition and individual quality. Birds in upper GR and CC and at Llagas Creek had higher mass, primary wear, and rectrice wear compared to birds in lower CC and GR. Bib size and fluctuating asymmetry of barbule density in rectrices was greater in birds located in CC and GR. Hue of bib feathers was significantly greater in birds caught at lower GR and CC and upper CC. Total mercury concentrations in rectrices were highest in birds caught in upper GR. All comparisons were significant with a p-value of less than or equal to 0.05.