USGS - Science for a changing world

What We Leave Behind

This Science Feature can be found at: http://www.usgs.gov/blogs/features/usgs_top_story/what-we-leave-behind/

When you go hunting or fishing, the gas in your car is unleaded but your ammo and tackle may not be. Even the most conscientious shooters and anglers may leave some of their ammo and tackle behind, and if it’s made with lead that could spell trouble for the birds that come along afterward.

There is copious scientific literature on the negative effects of lead from ammunition and tackle on wildlife. Nonetheless, the subject remains controversial among hunters and anglers. A team of scientists, led by USGS Wildlife Ecologist Susan Haig, recently published a new review of the literature on the subject.  Their publication explores the effects of lead ammunition and fishing tackle on birds and investigates various measures to reduce their exposure to it.  This information is critical to wildlife managers and outdoor enthusiasts who are trying to limit lead’s harmful impact on birds while also maintaining opportunities for hunting and fishing.

Why Lead?

Lead Core Bullet Samples

An unfired and fired lead core bullet (with a copper alloy jacket) fired into a water barrel from a .30-06 rifle. Photo courtesy of Clinton Epps, Oregon State University.

Lead is the metal of choice in ammunition and tackle because of its low melting point and malleability, and its cost compared to alternative metals.  In 2013 the USGS found that 69,000 metric tons of lead – that’s over 152 million pounds – were used to produce ammunition in the United States in one year. Annual estimates of lead fishing weights sold add almost another 9 million pounds. Together, that’s about one-and-a-half times the weight of the Titanic. Not all that lead ends up being left behind after every outdoor excursion, but some does.

According to Haig, birds ingest lead in different ways. Common Loons, for example, swallow lead sinkers and jigs, perhaps mistaking them for prey. Other birds eat lead pellets or fragments as grit to aid in digestion. Scavengers including condors and eagles often feed on carcasses of animals killed by hunters and subsequently ingest lead fragments.  The impacts can range from lethargy and anorexia to reproductive issues and even death.

Start with Science

The review, published in the August issue of The Condor: Ornithological Applications, summarizes decades of research from the USGS and other institutions on the sources and effects of lead ammunition and fishing tackle on birds. It includes research on the physiological effects of lead eaten by birds, the wide range of lead poisoning responses by different bird species and the effects on population numbers.

The scientists also introduce three priority research directions to better understand the threat of lead poisoning on birds.

Better measurements of variation in sensitivity to lead exposure among bird species.

Better understanding of what areas are affected by sources of lead contamination in relation to bird exposure in those same locations.

Examination of the interactions between lead exposure in birds and other landscape-scale factors that affect bird populations.

Diverse Efforts to Reduce Lead Exposure

Black-billed Magpies

Black-billed Magpies (Pica hudsonia) feed on mule deer (Odocoileus hemionus columcianus) shot near Penticton, British Columbia, Canada. Photo courtesy of Laure Wilson Neish.

Haig and her colleagues reviewed several different approaches to reduce birds’ exposure to lead from ammunition and fishing tackle.

Outreach is one approach. Haig says “Arizona Game and Fish joined with hunting groups to share information about the negative effects of lead on California Condors in the Kaibab Plateau region. One study estimated that over 80% of hunters switched to non-lead ammunition as a result, and no condors were found with lead poisoning the following year.”

Other approaches include regulations such as the Federal ban on lead ammunition for hunting waterfowl or state restrictions on the use of lead fishing tackle in certain areas. Successful approaches to reduce lead exposure in birds are most likely to come from wildlife professionals, hunters and anglers working together to sustain wildlife resources and society’s hunting and angling heritage.

“Fortunately,” Haig said, “there are some realistic and effective ways to decrease the danger of lead ammunition and tackle to birds and other wildlife.”

USGS Providing Sound Science

The USGS has long conducted research into the effects of contaminants on birds. The USGS Patuxent Wildlife Research Center, established in 1936, and the USGS National Wildlife Health Center, established in 1975, have been centers of expertise with enduring legacies in this field. The USGS Ecosystems and Environmental Health Mission Areas also support this research with many scientists across the country. The USGS is committed to helping Americans understand the impact lead poisoning has on wildlife. Communication among scientists, outdoor enthusiasts and policymakers will ultimately reduce the threat.

You can find out more information on contaminants and their effects on wildlife at the following USGS websites:

Wildlife and Contaminants Online

Contaminant Hazard Reviews On-Line

Whole Wildlife Toxicology Catalog

National Wildlife Health Center, Impacts of Lead on Wildlife

More Information

Review paper:  “The persistent problem of lead poisoning in birds from ammunition and fishing tackle”

Accompanying perspective publication: ”Considering the switch: Challenges of transitioning to non-lead hunting ammunition”

Oregon State University News Release