Research - Eagles and Lead
SOAR began gathering data in 2004 on the admissions of bald eagles to wildlife rehabilitators in Iowa. Eagle data includes: date of admission, cause for admission, gender, adult/juvenile, county found, lead levels from blood sample or liver or bone biopsy, and if euthanized, died, or released.
SOAR has also looked for the source of the lead, as able, through x-ray, CT scan, or fluoroscope image of eagles and other raptors that show symptoms of lead, and deer carcass and packaged venison. SOAR has documented eagles and other scavengers feeding on carcasses.
A Sad Full Circle
In 2006, this bird came in from Mills County with a band. She was banded as nestling in Shell, Missouri in 1986! She had a fractured humerus -- which Ross Dirks, DVM, at Dickinson County Animal Clinic, Spirit Lake pinned. The wing healed nicely, she spent eight weeks in intensive care. After one month in the 100 foot flight she is ready to go. Kathy Hodges releases her on our farm in honor/memory of her son Drew, who had just died from cancer.
In March 2009 a call from the warden in Mills County, has a dead eagle with a band -- yes our baby. Liver biopsy showed lead poisoning as cause of death. She was 23 years old and in perfect feather.
What did she likely eat in February or March 2009? Yep, she probably had been feeding on a gut pile or a deer that had been shot with a lead slug and not found by the hunter.
How could this death have been prevented? One - the hunter found the shot deer and field-dressed, the gut pile was buried or bagged and taken home to be disposed of according to their local county/city regulations. Two - the hunter had used a non-lead slug.
How do we test for lead?
Testing for lead can be done two ways; blood samples and liver or bone samples. While the bird is still alive, blood samples can be taken and analyzed. Liver and bone biopsies are completed only after the bird dies. Test results can be expressed in parts-per-million (ppm) or micrograms per deciliter (µg/dL). For reference, 10 µg/dL = 0.1ppm.
Blood lead level test results and what they mean:
Under 0.1 ppm (<10 µg/dL) is background and is considered normal.
Between 0.1-0.2 ppm (10-20 µg/dL) is considered to indicate exposure to lead, would not be poisoning (i.e. lethal by itself) and may not require treatment.
Above 0.2 ppm (>20 µg/dL) is definite lead poisoning case.
Liver biopsy results and what they mean:
Less than 1.0 ppm is background and is considered normal.
Between 1.0 ppm and 6 ppm is considered to indicate exposure to lead, but not at the potentially lethal poisoning level.
Over 6 ppm is definite lead poisoning case.
Exposure to lead can cause the animal to be impaired and not be able to catch prey, have collisions, etc. so exposure levels are still potentially lethal indirectly.
Lead availability study
SOAR, in partnership with Whiterock Conservancy, conducted a field survey during the 2008 winter shotgun deer season to document the incidence, abundance, and distribution of available lead fragments in white-tailed deer carcasses harvested with lead slugs. Fourteen lead-slug-shot white-tailed deer carcasses and associated gutpiles were borrowed from cooperating hunters for x-ray. Click here to read the draft paper on this study. (437 KB PDF)
Cumulative bald eagle data 2004-2012
X-rays of eagles, deer, ground venison
This x-ray shows a lead fragment in the eagle, about where the stomach would be. X-ray provided by MacBride Raptor Project.
X-ray of a deer carcass that was shot with lead deer slugs, reveals that the main body of the slug traveled completely through the deer, but lead shrapnel fragments were left in the carcass at the points where the slugs passed through and shattered bone. This shrapnel looks quite similar to the irregular shrapnel pieces found in eagle digestive systems. In this x-ray of a deer's mid-section, you can see the lead fragments where the slug went through the ribs below the spine and grazed the top of the spine.
This is an x-ray of a pellet that was coughed up by an eagle just after having received fluids at admission. This eagle tested positive for lead poisoning.
Packages of ground venison were x-rayed for lead fragments.
The bright, white fleck in this x-ray of ground venison is lead.
Bald eagles and other large raptors are not only predators, but they also are opportunistic scavengers. What does this mean? Simply, an opportunistic scavenger is not likely to ignore a large carcass laying in a field or alongside the road. Field observations of eagles confirm their behavior of seeking out and feeding from large carcasses for several days at a time.
Yes, this is an eagle feeding station -- SOAR salvaged roadkill deer (with the necessary permit from an Iowa DNR conservation officer to pick up) and carp and placed in a field in Carroll County, along with a motion-activated trail camera. The dates on the photos are correct, but the time stamp is wrong. SOAR is, of course, very careful to examine carcasses to make sure there is no chance of lead. Please do not use butcher scraps from lead-shot animals or leave animals shot with any type of lead ammunition out for predators or scavengers to eat.
The Peregrine Fund hosted this conference in Boise, Idaho with the goal of the conference to promote a better understanding of spent lead ammunition as a source of lead exposure and to reduce its effect on wildlife and humans.
Bald Eagle Lead Poisoning in Winter; Abstract presented at The Peregrine Fund "Spent Lead Ammunition" conference (689 KB PDF)
Iowa Lead Advisory Group Action Plan (272 KB PDF)
SOAR received an Iowa Resource Enhancement and Protection – Conservation Education Program (REAP-CEP) grant to form a Lead in the Environment Advisory Group. This Advisory Group would bring together the stakeholders involved in the issue of lead in ammunition and tackle. Through meetings, focus groups, and discussion a plan of action to address this issue was formulated.
- Lead in the Environment - learn how lead affects the body
- Hunting Lead-Free & Saving Wildlife
- Other Research & Info
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