08/11/2026
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The necropsy, done by Bronx Zoo pathologists, found four different anticoagulant rodenticides in his system alongside a severe pigeon herpesvirus picked up from eating feral pigeons. The zoo's conclusion was that those two conditions would have been fatal on their own, even without the collision, and likely contributed to him flying into the building.
Second-generation anticoagulants don't kill quickly. The rodent stays alive for days, sluggish and out in the open, which is precisely the animal a hungry owl selects for. One dose rarely kills a bird that size. It accumulates. The chemicals stay in a bird's system for at least 100 days, and the Wild Bird Fund attributes roughly 84% of the poisoning deaths it sees to rodenticide.
Flaco wasn't the first. Barry, the barred owl who lived in Central Park, also had high rodenticide levels when she was hit by a truck in 2021, and the levels may have affected her flying.
For a homeowner, the swap is snap traps in enclosed boxes. Same rodent removed, nothing left circulating for the next animal that eats it.