Mercury (Hg) is a pollutant that has become a large threat to many ecosystems and the organisms that live within them. Mercury is a known neurotoxin that can cause extensive central nervous system damage, which can impact the behavior and survival of many species. Inorganic mercury is often deposited into the atmosphere by anthropocentric sources and can easily enter water sources through precipitation. These inorganic forms of mercury are then methylated by phytoplankton or bacteria in anoxic environments, creating an organic form of mercury called methylmercury (MeHg). Methylmercury accumulates in individuals and easily moves up through the trophic levels. As a result, the bioavailability of methylmercury in anoxic environments becomes a pressing issue within aquatic food chains. Riparian songbirds, due to their mixed diet and the fact that they occupy both aquatic and terrestrial habitats, are often used to monitor methylmercury availability within these environments, but very little is known about how territory location can influence Hg exposure. The goals of this study were to record territory size and location for a suite of riparian songbirds and to sample songbirds to test for individual Hg exposure.
Results/Conclusions
In June and July 2018, we studied riparian songbirds at two sites in Acadia National Park: Gilmore Marsh near Aunt Betty Pond on Mount Desert Island and an unnamed beaver pond on the Schoodic Peninsula. Over the course of seven days, we collected GPS coordinate points of focal riparian songbirds at locations where they were heard singing or seen foraging. These GPS points were compiled into territory maps to understand how much of their territory was within the riparian zone. We sampled a total of 22 individual songbirds for blood Hg. Mercury concentrations ranged from 0.065 ppm to 0.485 ppm (ww). Preliminary analysis shows that bird with territories further from the water edge had generally lower Hg concentrations. Understanding how mercury exposure varies on an individual level is important to understand how to protect birds from this contaminant. Fecal samples were also collected so that the diet of riparian songbirds can be assessed and compared with mercury concentrations.