By Katherine Patterson
Watertown Resident
On Sunday, January 11th, we were amazed to see a beautiful barred owl sitting on a low branch in our backyard. We live next to Whitney Hill in Watertown, and had been hearing barred owl calls in the evening over the past few weeks (“who cooks for you?!”).
After an hour our excitement turned to concern. The owl was now completely still, unbothered by any nearby noises.
We tried to reach a wildlife rehabilitator, with no luck. We spoke with the Massachusetts Environmental Police, and though they shared our concern, they could not come out for the owl.
As the afternoon light began to fade, we noticed the owl had left. Our relief was short lived, as we soon spotted its body face down on our stone wall. It had literally fallen out of the tree dead.
The people I had connected with to try and get help for the owl told me there was a good chance that the owl had suffered secondary poisoning from anticoagulant rodenticides, unfortunately a common cause of death for owls, raptors, coyotes, and foxes. There are several well-publicized cases of this, including a family of great horned owls, the bald eagle MK in Arlington, and Flaco the escaped Eurasian eagle owl in New York City.
I wanted to know whether the owl in our backyard had suffered from rodenticide poisoning, but most wildlife centers I called said they unfortunately cannot test every animal. They are very aware of what a huge problem it is. A 2020 Tufts Wildlife Clinic study tested samples from 43 red-tailed hawks in the northeastern United States and found anticoagulant rodenticides present in ALL of them.I have since learned more than I ever wanted to know about rodent poisons.
Anticoagulant rodenticides (second-generation anticoagulant rodenticides, or SGARs, are potent and commonly used) can take up to 10 days to kill a mouse or rat. As the rodent slows down and becomes ill, they are easier prey. Though eating one poisoned rat will not kill an owl, raptor, fox, or coyote, the anticoagulant rodenticide accumulates in the body of the predator. These toxins build up after each exposure, leading to chronic illness, immune system suppression, and eventually a long and painful death.
Secondary poisoning of the very animals that help to control rodent populations CAN be avoided. Integrated pest management strategies are straightforward and effective:
First: Block rodents (seal up entrances, use non-toxic repellents).
Second: Starve rodents (remove trash and food sources).
Third: Use non-poison methods to remove rodents (snap traps, carbon dioxide sprayers, etc).
Finally, if poison is needed for a serious infestation, cholecalciferol (vitamin D3) can be used instead of an anticoagulant rodenticide. Cholecalciferol does not cause secondary poisoning in predator species.
Many Massachusetts towns and cities have organized around this issue and no longer use anticoagulant rodenticides on municipal property. Watertown’s stated policy is to follow an integrated pest management strategy, and to use the vitamin D3 formulation in bait boxes on any municipal property. There is currently legislation in the Massachusetts Senate to more carefully regulate anticoagulant rodenticides on the state level, which will limit the use of these rodenticides by licensed exterminators on private property as well. Save Watertown Wildlife is active on this issue, and the Mass Audubon Rescue Raptors program has been supporting these efforts across the state.
The body of the barred owl from our yard is now waiting in a freezer, and at some point I will drive it to Gloucester to be tested for SGARs. Regardless of the outcome of that test, I am committed to protecting the predator species that we are lucky enough to call our neighbors.
A few nights ago, while walking my dog, I heard another barred owl in Whitney Woods. I sat down to watch, and it flew closer. Eventually the owl perched on a branch directly above us. At this point I was talking to it continuously, somewhat nervous that it might dive bomb my dog! After carefully inspecting us for a few moments, the owl flew off.
When I got back inside and into the light, I realized that the owl had pooped on my dog’s head. I’m taking that as a sign from the raptors to keep working on this issue.
