American Kestrel Nest Box Plans

For more information and to start your own nest box monitoring:

The Silent Killer!

An increasing number of raptors are exposed and dying from rodenticides, commonly called “rat poison”. Unsuspecting people that wish to control or rid their property of rodents often turn to products, such as D-Con; however, this choice comes at a high price. When the targeted animal eats the poisoned bait, it does not die immediately. This potentially deadly prey animal now runs the risk of being caught and eaten by a non-targeted animal such as a raptor. Raptors that do well in an urban environment, such as Red-tailed Hawks (Buteo jamaicensis) and owls, are at a higher risk.

Companies that manufacture rodenticides try to counteract a bad public image by marketing the product as safe and that the poisoning of non-target animals is rare. Below is a direct response from D-Con’s website to the question of whether the product could poison unintended animals: (
The potential of any secondary poisoning depends on what type of pet it is, how big it is, what type of bait it has consumed, as well as how much bait was consumed. If you are concerned about a possible exposure, you may wish to contact your veterinarian or the toll free number located on the package to be directed to appropriate personnel who can address your concerns. Occurrences of this type of poisoning are extremely rare.”

They admit that smaller animals are at greater risk. An adult Red-tail weighs two to four pounds and an adult Great Horned Owl (Bubo virginianus) two to three pounds. The preferred prey for these species are small mammals, such as mice and chipmunks, are high targets for rat poison.

Anticoagulant rodenticides (AR) affect the vitamin K-mediated synthesis of blood clotting factors in the liver. The animal eats the poisoned prey and becomes at risk for fatal hemorrhage episode triggered by trauma and/or increased heart rate. Second generation anticoagulant rodenticides (SGAR) stay in the body longer than its first generation, making it more lethal (Stone et al. 2003).

A recent study revealed a high percentage of Red-tails and Great Horned Owl have residual levels of rodenticides stored in their liver (Stansley et al. 2014). The researchers collected liver samples from Red-tailed Hawks and Great Horned Owls in New Jersey. At least one SGAR was detected in 81 % of Red-tailed Hawks and 82 % of Great Horned Owls. The most frequently detected SGAR was brodifacoum, which was detected in 76 % of red-tailed hawks and 73 % of great horned owls. According to ((ABC) 2013)Brodifacoum was made a “restricted use” pesticide in 2008 by EPA, meaning it can only be used by certified pesticide applicators. The manufacturer of D-Con (household brodifacoum) is challenging this decision in court. The product remains on the market for public use.

Reading between the numbers and statistics, rat poison remains a very real danger for raptors. The bottom line, don’t use them! If you have a rodent problem, put up a kestrel nest box (download plans from our website) or barn owl nest box on your property. Please visit these websites for information:

Barn Owl Trust

Barn Owl Nesting Box Plans


(ABC), A. B. C. 2013. Pesticide profile - brodifacoum.

Stansley, W., M. Cummings, D. Vudathala, and L. A. Murphy. 2014. Anitcoagulant rodenticides in Red-tailed Hawks, Buteo jamaicensis, and Great Horned Owls, Bubo viginianus, from New Jersey, USA 2008-2010. Bulletin of Environmental Contamination and Toxicology 92:6-9.

Stone, W. B., J. C. Okoniewski, and J. R. Stedelin. 2003. Anticoagulant rodenticides and raptors: Recent findings from New York, 1998-2001. Bulletin of Environmental Contamination and Toxicology 70:34-40.

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