Recently a reader asked me to write about rodenticides. I thought writing about the history of the eagles at the Mystic Lakes would be a good way to demonstrate the effects of these poisons, which kill thousands of raptors each year. When I started writing, the mated pair at the Lakes, KZ and FAE, were both alive and well.
But tragedy struck last week. FAE, the female eagle, died, probably early in the morning on Wednesday March 11. Around that time, KZ was seen perched on a fence near where FAE’s lifeless body was spotted by a birder on Thursday morning. The Massachusetts Division of Fisheries and Wildlife (MassWildlife) took FAE’s body to the Tufts Wildlife Clinic in North Grafton, but toxicology reports might take weeks.
FAE did not show obvious signs of bleeding, which could indicate rodenticide poisoning, according to Paul M. Roberts, a Medford-based raptor conservationist, researcher and photographer. It’s possible FAE died of avian flu or another cause. But KZ’s previous mate died of rodenticides, and so did one of their eaglets.
Triumph and heartbreak
That there are bald eagles in our area at all is a triumph. The birds had become endangered across the state from hunting, habitat destruction and the use of the insecticide DDT. Their comeback started in 1972, when the Environmental Protection Agency banned the use of DDT in the United States. Then, from 1982 to 1988, MassWildlife and Mass Audubon acquired 41 bald eagle chicks from Canada and Michigan and raised them on platforms at the Quabbin reservoir. Caretakers used puppets to feed the eaglets so they would not imprint on their human handlers.
Our northern bald eagles become adults in four to five years, and in 1989, the first nesting eagle pair raised a brood at the Quabbin. In the following years, more eagles nested, and juveniles spread out across the state and into Connecticut and New York. Today bald eagles regularly visit Fresh Pond and Alewife Reservation.
MK and KZ arrived at the Mystic Lakes in 2019, where they nested and hunted year-round. KZ was born in 2015 in Webster, where wildlife biologists banded him. MK was born in Waltham in 2016. (Their names are the first two letters from their leg bands.)
In 2020 they hatched a pair of chicks, but 26C died from rodenticide poisoning. Their other eaglet (25C) was killed by a car in Delaware. In 2022, they hatched an eaglet, 46C, who is now a four-year-old young adult eagle and is occasionally seen in the region.
But, on February 23, 2023, people found a sick, lethargic MK at an Arlington cemetery, barely able to stand. MK had been poisoned by anticoagulant rodenticides (rat poison). Rodenticide kill in a terrible way; veterinarians at the Cape Wildlife Center in Barnstable tried to save her, but she began to bleed internally. The poison meant her blood would not clot, and it blocked her airway. She coughed up blood, as her heart slowed. MK died in minutes.
FAE joins KZ
After KZ lost his mate, a new unpaired female moved in almost immediately. She was not banded, so her origins are uncertain. She became known as “female adult eagle,” or FAE.
In 2024, KZ and FAE raised three eaglets. Two died within weeks of leaving the nest. The third, 91C, broke a wing but was rehabbed and released. The pair again produced three chicks in 2025: females 75C and 76C, and a male, 77C.
Eagle parents share responsibility for feeding their young. KZ began delivering fish, some so heavy he had to rest before lifting the meal 50 feet up into the nest. When fish were hard to find, the eaglets were given squirrels, rabbits, and even a raccoon.
After the youngsters left the nest, FAE and KZ continued bringing them food, gradually providing less to encourage their offspring to hunt on their own. Young eagles sometimes leave for other environs, as KZ’s earlier offspring, but they could spend the next two years in our area, socializing with other juvenile eagles and ignored by the adults. However, once they are old enough for adults to see them as threats, they will not be well tolerated.
KZ not a widower for long
This past Wednesday, when KZ returned to the nest, a salt-and-pepper colored three-year-old female eagle popped up from the nest. She had entered the nest within 10 hours of FAE’s death.
On Thursday morning before sunrise, Roberts spotted KZ cavorting and mating with the new unbanded eagle he calls SALT, for the white spots on her back, underwings, and breast. Are the two eagles now an item? It looks that way. But eagles usually lay eggs from mid-February to mid-March, so there is no time to waste if they have any hope of reproducing this year.
But like all birds and indeed, any animal that might prey on rodents, they face a continued threat from anticoagulant rodenticides. Many scientists think that rodenticides are worse than DDT because of their extreme toxicity and high rate of secondary poisoning in predators.
Unfortunately, rodenticides do not appear to reduce rat populations. When rat numbers decline, the females reproduce more, so the population rebounds quickly. The most effective way to reduce rat populations is reducing their food supply. This might mean composting food waste. It certainly means doing something about dumpsters that are rat (and bird and squirrel) food emporiums. And we could push for a ban on rodenticide use. Cambridge has banned second-generation anticoagulant rodenticides (SGARs) on city property, and the state is considering legislation to phase them out, as well.
Thanks to Paul M. Roberts, who provided much of the information in this article.
Photo link
Captions/credits
1. FAE the bald eagle, who recently died of unknown causes. (Margaret Lewis)
2. MK and KZ at the Mystic lakes, May 2022. (Margaret Lewis)
3. KZ and SALT, named for the white spots on her back, March 13, 2026. (Paul M. Roberts)
4. A juvenile bald eagle at the Mystic lakes captures a rodent, February 11, 2023. (Karl Niemi)
5. A juvenile bald eagle on Fresh Pond, January 9, 2022. (Richard George)
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