A sentinel species is an animal used to detect risks to humans or the environment. These species are particularly sensitive to changes in their environment—such as pollution, toxins, or disease—and their health reflects the overall condition of the ecosystem they inhabit.
Loons and eagles are considered sentinel species in Canada's freshwater environments.
Loon life expectancy is 15-30 years. Their long lifespans are crucial for maintaining stable populations because they take years to reach maturity and typically only have a few offspring in their lifetime. But when a loon ingests lead —mistaking it for a stone or swallowing it with a fish—the consequences are often fatal.
Loons do not mate until they reach the age of 6-7 years of age.
A pair averages 1/2 chick per year—if any survive. This low reproductive rate means that even small increases in adult mortality can have major effects on loon populations. When breeding adults die from ingesting lead tackle, it’s not just a loss of one bird—it’s the loss of years of future offspring.
A New Hampshire study found that 49% of adult loon moralities were caused by poising from lead fishing tackle specifically!
Other studies in Ontario and across North America have identified lead poising from ingested fishing tackle as the leading cause of death in loons and 78 other species, including bald eagles, great blue herons, swans, ospreys, mallards and mergansers.
Many other waterbirds—such as swans, ducks, eagles, and herons—are also at risk. These birds can accidentally ingest lead while feeding on the lake bottom, mistaking them for grit. Raptors like eagles and ospreys, and aquatic mammals like otters and minks, may also suffer lead poisoning after eating fish or waterfowl that have ingested lead. Even some frogs, turtles, and fish can also be affected. Lead fishing tackle isn’t just a threat to loons—it’s a threat to the entire freshwater ecosystem.