Why Are We Still Killing Loons with Lead Sinkers?

In the interest of full disclosure, I will admit that I am grouchy. In the past five days, we have lost three adult loons from our study area. The first of these was the Arrowhead Lake male who, having broken his right wing in early July, finally succumbed to that injury last Friday, leaving his mate and two almost-grown chicks. We all knew that the Arrowhead male was going to die before the end of the season, but it still hurt when his lifeless body finally washed ashore.

The second loon that we lost was an adult male found in the eastern part of Minocqua Lake. He was unbanded, and the only unbanded male we know of from that location is the territorial male from the Minocqua-East territory, who nested unsuccessfully with his mate in the thoroughfare to Lake Tomahawk in May. So we are fairly confident that this male is from Minocqua-East. On Saturday he became incapacitated, beached himself near the Minocqua boat landing, was reported by lake residents, and was picked up in this defenseless condition by Linda and Kevin Grenzer, who took him to Raptor Education Group, Inc. Linda and Kevin could tell from his green droppings and lethargy that he was likely a victim of lead poisoning, and their suspicion was confirmed by a blood test at REGI on Saturday. The folks at REGI started chelation treatment to remove the lead from his blood, but their efforts were too little, too late. A large male weighing about 4.5 kilograms when he was healthy, he had wasted away to 3.1 kg at his death.

Male from Katherine Lake on Lake Michigan. Photo by Christopher Rocke.

The third death of a male loon from the study area occurred just a day later. On Sunday Chris Rocke e-mailed me to say that while paddle-boarding on Lake Michigan, he had run across a marked loon that stayed very close to shore (see his photo, above) and seemed reluctant to dive. He became concerned about the bird’s odd behavior and listlessness. Over the few days that Chris watched him, this loon became weaker and weaker, to the point where Chris was able to capture him by hand on Sunday afternoon. His bands, photographed by Chris, below, showed that he was “silver over red, taupe-stripe over red”, an individual that we have come to know well over the

years. First banded in 2004 on Lake Seventeen with his mate and two chicks, this male and the four females he was paired with during his breeding career on Seventeen cranked out eight offspring before his eviction in 2014. He then relocated to Katherine Lake, where he nested unsuccessfully for six straight years. This year, he and his mate failed in a way that we had not observed previously — first one of their eggs and then the other rolled off into the lake, because the nest had been placed on a slope near the water. Still, this male’s breeding success on Seventeen made him one of the most productive breeders in the study area. Like many loons from the Upper Midwest, he was making a stop on Lake Michigan prior to completing his migratory journey south.

Once I learned that Chris had found one of my oldest and most familiar study animals in a compromised condition, I urged him to take the loon to an animal rescue center. Chris and his partner, Leva Engel, interrupted their Labor Day vacation, drove the Katherine male over an hour towards Antigo, and dropped him off with Linda and Kevin Grenzer, who completed the trip to REGI. As the featured photo shows, it was deja vu for the Grenzers: another limp, lethargic loon. This condition, together with his greenish feces, pointed again to acute lead poisoning, a diagnosis confirmed by blood test. Like the Minocqua male that had died the day before, the Katherine male’s lead concentration was so high that it could not be measured precisely. The Katherine bird had wasted away from 4.4 to 2.8 kg in a period of a week or so, owing to his inability to feed himself. After several seizures yesterday (another symptom of lead poisoning), he passed away overnight.

If lead poisoning were a freak occurrence, like a lightning strike, we could justifiably shrug and move on. We cannot protect loons from lightning strikes. But a clear pattern has developed in northern Wisconsin: many adult loons die each year from acute lead poisoning, when they ingest lead sinkers, usually on fishing lines. Loons can survive ingestion of fishing tackle. In fact, their powerful digestive systems have been shown to grind up steel hooks and swivels. Lead is different. Lead kills loons, eagles and other wildlife that swallow it, because it has rapid, powerful effects on the brain and nervous system and cannot be quickly broken down or expelled by the body. And most loons that ingest lead fishing tackle are not reported by humans until they are so weak that even extreme measures taken by veterinarians cannot save them.

Consider this. We hear about only a fraction of all loons in Wisconsin that swallow a lead sinker and die quietly on a lake shore. Still, in the time since I started this blog, we have recorded five loon deaths (three just this year) from lead poisoning. I think it is time to see lead poisoning as less of a freak occurrence and more of a regular — and probably important — source of loon mortality. In New Hampshire, half of all recorded loon deaths in a 2017 study were caused by lead toxicosis. Even if we are far better off in Wisconsin, and only, say, 1/4 of all loon adults die from lead poisoning in our state, this seems like an unacceptable number. I say this because we can prevent deaths of loons, eagles, and other wildlife simply by using fishing sinkers made of bismuth, tungsten, steel, or other materials. In short, at a time when the population of loons in northern Wisconsin is already in trouble, why are we still using fishing tackle that kills loons?