Causes of mortality and unintentional poisoning in predatory and scavenging birds in California

Birds were collected from wildlife rehab centers. Practically all predatory birds are impacted by rodenticides. Mortality of birds submitted from rehab centers between 2007 & 2009 were caused by: collisions (63%), lead poisoning (17%) and anticoagulant rodenticides (8%). However, these percentages are misleading because birds with broken wings are more likely to find their way to a rehab centers than a bird that is slowly dying  from poisons but still mobile. Study conclusion: Knowing causes of deaths in predatory & scavenging species provides important data to help regulatory agencies be better informed about threats to species of birds that are vulnerable. CDF&W has compiled a long list of birds who have died due to eating prey animals laden with rodenticides. Golden eagles, Peregrine falcons, many species of hawks and many species of owls are particularly vulnerable.

Take home: 25 to 49% of birds tested had elevated levels of lead in their livers and 84% had detectable rodenticide residues. Sampling was skewed towards testing birds with physical injuries because birds with injuries are more prone to find their way to rehab centers than sick but mobile birds.

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