Unusual Level of Mammal Predation by a Pair of Peregrine Falcons (Falco peregrinus)

During the 2023 and 2024 nesting seasons, we observed a pair of Falco peregrinus (Peregrine Falcon) in Woburn, Middlesex County, MA, preying upon and eating an unusual number of terrestrial mammals. These included 3 Rattus norvegicus (Brown Rat), 4 juvenile Sylvilagus floridanus (Eastern Cottontail), with a failed attempt to capture another, and a Blarina brevicauda (Northern Short-tailed Shrew). Since Peregrine Falcons are considered avian prey specialists, they are not usually thought to be in jeopardy of exposure to anticoagulant rat poisons. However, these falcons were observed eating at least 3 Brown Rats captured within 30 m of observed active rat-poison bait boxes, and nesting in the same Corvus corax (Common Raven) nest in which an adult raven was observed dead on eggs in 2016, consistent with a Massachusetts case of confirmed Haliaeetus leucocephalus (Bald Eagle) mortality from anticoagulant rat poison. As of September 2025, both adult falcons are still alive, but are at continued risk because the toxins used in anticoagulant rat poisons are cumulative.