Contaminants

As top avian predators, raptors can be particularly sensitive to environmental contaminants through bioaccumulation/biomagnification of toxins they come into contact with through their diet. An example of the catastrophic effects contaminants can impose on wildlife and the environment was the indiscriminate spraying of the pesticide DDT (dichlorodiphenyltrichloroethane) in the 1940s-1960s. The pesticide nearly drove Bald Eagles, Peregrine Falcons, and Swainson's Hawks to the brink of extinction. While American banned DDT in 1972, the pesticide is still used in areas of South America and continues to effect certain raptor species. HWI understands the sever threat contaminants can have on raptors, and vigilantly monitors the changing landscape of synthetic chemicals and conducts research to counter their negative effects.


Mercury Contamination

Mercury cycle 523X309 nmtracking orgMercury is an increasing problem globally, with the Great Salt Lake being a particular mercury hotspot. Mercury concentrations in the lake itself are among the highest ever recorded for a North American water body, as are some of the concentrations found in some species of waterfowl and shorebirds that pass through each year for multiple months as a migration stopover to fatten up on brine shrimp before heading farther south. Research has shown they accumulate mercury during this time, most likely derived through the contaminated brine shrimp diet they ingest at the lake. More research is needed, but the implication is that the Great Salt Lake has become a regional driver of mercury contamination via export through the Eared Grebes and millions of other birds that spend significant amounts of time here (waterfowl, shorebirds, song birds, etc.). Hence, the Great Salt Lake is not simply a local mercury hotspot, but rather a source for much broader environmental contamination that may have ecological impacts on a broad front, with potential wildlife and human health impacts. One problem is that while mercury research has been conducted on a few avian species here and there (e.g., Loons, Eared Grebes, Bald Eagles, and various waterfowl and gulls), there are large numbers of species with no information on their exposure levels to contaminants; furthermore, even less is known about the specific level of mercury that harms reproduction or health of individual species, so we don't know to what degree species or populations are being impacted.

HWI is currently collecting feather samples from Peregrine Falcons and the prey species they feed on to look at mercury contamination by using "top-down" monitoring to inform us about contamination on an ecosystem level. While the same statement could be used for many raptors/predators, Peregrines are particularly useful as an indicator species because they have a huge breeding distribution, nearly global, across a large number of habitat types (e.g., aquatic, alpine, open desert, temperate forest, tundra). They also feed on a very large number of bird species, which means they essentially sample mercury from a wide range of sources. Our current research is working to establish a baseline contaminant level in Peregrines (using Prairie Falcons for additional comparison) in northern UT, mostly around the Great Salt Lake and Wasatch Front area, but also extending into the West Desert. View our Peregrine Falcons as Ideal Mercury Biomonitors poster.

 

Lead Poisoning

Many animals are exposed to the hundreds of tons of lead hunting ammunition and fishing tackle that are deposited in the environment every day. Feeding atop the food chain, raptors and other predators can experience secondary lead poisoning when scavenging on contaminated carcasses or preying on animals that have been wounded by hunters. Raptors have highly acidic digestive tracts that easily erode lead that then absorbs into the blood stream, causing reproductive impairment, immune suppression, tissue damage, and death. While lead-based ammunition and tackle have been partially regulated in North America over the years, it is still the primary material for ammunition used to hunt mammals and upland birds, and for weights used to fish; much work remains to be done to reduce this major threat posed to wildlife. To address this problem, HawkWatch International started a public education program in Utah to encourage hunters and fishers to voluntarily explore lead-free ammunition and tackle by providing information on the damaging effects of lead on non-target wildlife and on the benefits of nontoxic alternatives. View our Wildlife Without Lead hunting brochure, and our Wildlife Without Lead fishing brochure.