Lead exposure of North American raptors

Lead is an anthropogenic threat to terrestrial wildlife, has no physiological benefits, and is considered a neurotoxin. Legislation adopted in many developed countries restricts the uses of lead in consumer and industrial products such as pipe fittings, petrol, paint, and shot for use in waterfowl hunting. However, lead is currently categorized by the United States (US) government as a critical metal and common uses of lead still persist in North America. These include the use of rifle ammunition, shot in upland gamebird hunting, and fishing sinkers. Lead is also a by-product of multiple industrial operations including smelters, coal power plants, oil refineries, and battery production facilities. As a consequence, there is regular deposition of potentially toxic amounts of lead in the environment. Anthropogenic lead influences the ecology and demography of multiple wildlife taxa, including a large number of avian species. Elevated lead concentrations are documented in avian scavengers as a result of ingesting lead fragments from hunter harvested animal carcasses. However, multiple forms of lead deposition exist in eastern North America, making the region ideal to study the pathways of lead exposure in wildlife. I documented the sources and pathways of lead exposure of raptors by studying novel species, seasons, regions and spatial scales. During the breeding season in the Chesapeake region of Maryland and Virginia, I found differences in blood lead concentrations among age groups of bald eagles but no difference between age groups of osprey. In the central Appalachians, I found that territorial red-shouldered hawks had higher blood lead concentrations in urban settings when compared to non-urban settings during the breeding season. I found that a community of facultative avian scavengers in eastern North America exhibited higher blood and liver lead concentrations during the fall and winter months compared to the spring and summer months when they scavenge to a lesser degree. On a nationwide scale, I found that 47% of bald eagles and 46% of golden eagles had femur lead concentrations above the threshold commonly accepted to indicate clinical lead poisoning. This work will provide information useful to the management of lead-influenced wildlife and identify potential opportunities for mitigation of environmental lead exposure and, using wildlife as sentinel species, help to understand potential human health hazards of lead exposure