Among popular American movies “On Golden Pond” stands out for a couple of reasons. The cast included film greats Katharine Hepburn and Henry Fonda in what was his last screen acting job. And, among other things, the story accorded a role to wild birds, namely loons.
The 1981 movie was filmed on and around Squam Lake, a 6,700-acre water body in central New Hampshire where, in fact, loons had long had a remarkable presence.
Indeed, loons and their haunting calls had such an enduring place in Squam’s habitat that it came as a real shock a little more than a dozen years ago when their numbers declined dramatically; in 2017, in a real shocker, only one loon chick hatched on Squam — the lowest number of hatchlings since monitoring began in 1975.
Research has turned up several potential causes for poor egg development, including high levels of chemical contaminants in the lake’s waters. The pollutants included DDT (which had banned from the marketplace in 1972) , PCBs and chemical components in flame retardants, stain repellants and other modern products.
Loons’ diet is principally fish, hence the birds are near the top of the food chain where they absorb contaminants that get into fish. The effect has been eggs that aren’t viable.
In this light loons are a bio-indicator, in sort of the same way that aquatic bugs tell us whether stream waters are clean by their existence in them.
But the disappointing experience in Squam is mysterious, because the loon situation there isn’t being duplicated elsewhere. Other Northeastern lakes aren’t seeing loon populations decline as they have in Squam – a lake whose water has long thought to be pure.
A couple of years ago New Hampshire journalist David Brooks described some of the problem in his Granite Geek column.
Research continues, the latest example being a report that came out last month under the title “Squam Lake Loon Initiative” by the Loon Preservation Committee.
Other loon studies of national scope are being carried out by the Maine-based Biodiversity Research Institute under the program title Restore the Call.
Here’s a fresh report on restoration of loons following an oil spill in Rhode Island.
Having said all this, water pollution isn’t the only threat to loons. Lead fishing tackle also poses a significant danger, which is why use of lead sinkers has been banned. But the birds may still be ingesting lead fishing tackle that was lost years ago – a reminder that humans’ impact on nature can be harmful long after corrective steps are taken.