It’s happened again. An urban Red-tailed Hawk that won the affection of many has been killed by poisons intended for rats.
In this case, the victim was Ruby, a plucky female that in the spring of 2010 chose the seventh-floor ledge of an office building across from Fresh Pond Mall in Cambridge, Massachusetts, as her nest site.
Delighting onlookers, she and her mate Buzz raised three offspring that year (nicknamed Lucy, Larry, and Lucky). The hawks nested successfully in the same spot the next three springs, so hopes were high again this year, but Ruby was found lifeless under her nest tree in early April.
Susan Moses, a Cambridge resident who made almost daily visits to the hawks’ nest since 2010, found the carcass and brought it to the Tufts Wildlife Clinic at Cummings School of Veterinary Medicine in North Grafton for necropsy, where veterinarians detected signs of lethal rodenticide poisoning.
Additional blood tests subsequently confirmed the presence of three different types of second-generation anticoagulant rodenticides (SGARs), substances the Environmental Protection Agency has recently moved to regulate more strictly.
Christopher Leahy, Gerard A. Bertrand Chair of Natural History and Field Ornithology at Mass Audubon, told the Boston Globe that Ruby had probably eaten a rodent contaminated with the poison at Mount Auburn Cemetery, a popular hunting area for wildlife in West Cambridge. The cemetery does not use the poison, but some local businesses are believed to use it.
SGARs were the primary compounds found in three Red-tailed Hawks found dead in New York City in February and March 2012. One of the hawks was Lima (also known as Ginger), a mate of Pale Male, the Red-tail that gained fame in the early 1990s, when it nested on an apartment building overlooking Central Park.
“Ruby had high concentrations of an SGAR called brodifacoum in her system and trace amounts of two other poisons,” said Dr. Maureen Murray, a wildlife veterinarian and faculty member at Cummings School. “While these poisons are meant to kill rodents, they have unintended consequences of harming and killing animals that prey on rodents. Sadly, wildlife is often overlooked in the age-old battle of human versus rodent.”
Ruby Memorial Research Fund
Hoping to raise $10,000 for research to monitor the health effects of rodenticides on birds of prey, Susan Moses asked the Tufts Wildlife Clinic to establish the Ruby Memorial Research Fund.
“We really hope people donate to this worthy cause and support the efforts of Cummings School,” she said. “What better tribute to Ruby than to fund research that will affect policy change on both the local and national level, and that we hope will protect future generations of raptors from dying needlessly from rodenticide poisoning.”
Murray has studied rodenticide poisoning in birds of prey for years and published research in 2011 that the EPA has cited frequently (abstract). The paper showed anticoagulant rodenticide residues in 86 percent of 161 birds that were tested over five years at the Tufts Wildlife Clinic. The study examined four species of birds — Red-tailed Hawk, Barred Owl, Eastern Screech-Owl, and Great Horned Owl — and found that, of those that tested positive, 99 percent had residues of the SGAR brodifacoum.
SGARs are more potent than their first-generation cousins. Rodents and other species need a much smaller amount of the poisons to suffer their effects. Another danger of SGARs is their ability to accumulate in liver tissue over time.
While this factor doesn’t necessarily make second-generation poisons more lethal for rodents than first-generation products, it has devastating consequences for wildlife. A Red-tailed Hawk that repeatedly feeds on prey containing sub-lethal amounts of the second-generation poison, for example, is at risk for accumulating a lethal amount over time.
In light of high numbers of children accidentally exposed to second-generation rat poisons as well as the risk to wildlife, the EPA tightened the safety standards for consumer use of household rat and mouse poisons in 2011. After a prolonged battle with the EPA, the last manufacturer to comply with the safety standards agreed in May to stop producing its second-generation poisons for sale to residential consumers by the end of the year.
“Until SGARs are phased out completely, consumers may still find a variety of poisons on store shelves,” said Murray. “So it’s very important to understand the larger ramifications of the products used in the home because of their potential harm to children, pets, and wildlife. The goal of our research is to continue to educate the public on this issue and monitor any long-term changes in rodenticide exposure in birds of prey as a result of the new EPA regulations.”
Read the abstract
Maureen Murray, 2011, Anticoagulant rodenticide exposure and toxicosis in four species of birds of prey presented to a wildlife clinic in Massachusetts, 2006-2010, Journal of Zoo and Wildlife Medicine, Vol. 42, No. 1 (March): pages 88-97. Abstract.