We are well aware that lead poisoning in humans can be very harmful. It is no different for birds of prey. Lead poisoning in birds of prey is a frequently fatal condition caused by ingesting lead fragments from ammunition in carcasses or from fishing tackle. The acidic, grinding environment of a raptor's gizzard dissolves these fragments, absorbing toxins that cause neurological damage, paralysis, and death, often following symptoms like weakness, green diarrhea, and inability to fly.
Source: Montana Raptor Conservation Center
Where does the Lead come from?
Raptors, especially scavengers like bald and golden eagles, ingest lead ammunition fragments (from bullets) or fishing sinkers present in carcasses, particularly during winter. Lead rifle bullets often shatter upon impact, dispersing hundreds of small fragments through a carcass or gut pile.
What is the Physiological Impact?
Once ingested, lead is absorbed into the bloodstream, causing acute or chronic toxicosis. It acts as a neurotoxin and impacts the gastrointestinal and renal systems.
What are the Symptoms?
- Behavioral/Physical: Lethargy, weakness, droopy wings, blindness, inability to stand, and head tilting.
- Digestive: Green-stained feces, vomiting, and paralysis of the digestive tract, leading to emaciation.
- Neurological: Seizures, convulsions, and incoordination.
How is Lead Poisoning Diagnosed and Treated?
Veterinarians use x-rays to detect lead particles in the gizzard and blood tests to measure lead levels. Treatment involves chelation therapy (e.g., CaEDTA injections) to remove lead from the blood, along with supportive care.
What is the Impact on Overall Populations?
Lead poisoning is a major, yet preventable, cause of mortality. It can significantly impact population growth rates, particularly for species like the golden eagle. Past reports have shown nearly 50% of eagles in the U.S. have an unhealthy amount of lead in their systems. Wildlife experts warn lead exposure continues to sicken and kill eagles each year.
How can we prevent it?
The primary preventative measure is switching to non-toxic ammunition (e.g., copper) and fishing tackle.
Resources:
University of Minnesota College of Veterinary Medicine The Raptor Center Research
Montana Raptor Conservation Center Lead Poisoning Information