Twin Ports gulls face unusual affliction
An unusual vitamin deficiency first discovered in birds in Europe may be striking down gulls in the Twin Ports harbor, wildlife rehabilitation experts say, and it appears to be killing Great Lakes fish as well.
Several ring-billed gulls found in the Twin Ports have been treated at Wildwoods wildlife rehabilitation center in Duluth, cured with a shot of vitamin B1.
It’s not known how many birds are dying and are never found, but already this summer four sickly gulls have been revived with vitamin B1 at the wildlife rehab center.
Last year more than a dozen gulls were brought to the center, many of them showing the same signs — unable to flap wings, unable to make any noise, listless and underweight — said Peggy Farr, head wildlife rehabilitator at Wildwoods.
“We’ve been getting them in for years, usually this time of summer, and it’s usually juvenile birds. It’s been the same thing. They are unharmed; no sign of trauma, but nothing we did would help. They’d get weaker and weaker and then keel over dead,” Farr said.
It wasn’t until last year that Farr found research from Europe, mostly Sweden, which described the same symptoms in gulls traced to a deficiency of thiamine, or vitamin B1.
“I started giving them a shot of B1 and it’s almost instant; in a matter of hours they are ready to fly,” Farr said.
That’s what happened to a listless gull found Thursday at the door of the Wisconsin Sea Grant office on Barker’s Island in Superior.
“One of its wings was just hanging; he couldn’t hold it up. (The wing) looked broken or hurt. The gull walked up and on the sidewalk like it didn’t know where to go,” said Mary Munn, who first discovered the sickly bird.
When she and Sea Grant co-worker Marie Zhuikov later went to assist the gull, “I could just reach out and grab it. It didn’t even try to get away,” Munn said. “It opened its mouth, but no sound came out. And it didn’t weigh anything, like it was dehydrated. It was in pretty bad shape.”
They brought the bird to Wildwoods. By Friday, Farr said, the gull had fully recovered and was released.
“We don’t know what’s causing this or how widespread it is. But we do know how to treat it now,” Farr said.
Chris Balzer, area wildlife manager for the Minnesota Department of Natural Resources, said he’s heard of no major gull die-offs in the Twin Ports — “or any sickly ones for that matter,” Balzer said.
The affliction apparently first was noted in gulls in the Baltic Sea area in 1983. It has been widely documented in southern Sweden, where the problem is so bad that the federal government has been asked to investigate. Several other wild birds also appear to be suffering from the thiamine deficiency, according to researchers at Stockholm University, including starlings and eiders.
Thiamine is an essential nutrient for birds and other animals, including humans. Thiamine deficiency was found in the eggs, livers and brain of afflicted gulls, and those gulls were revived with thiamine treatment — essentially a shot of B1.
Researchers say something, such as a chemical, may be blocking the birds’ ability to absorb thiamine from their food or that the thiamine may be missing from their food altogether — something may be keeping it out of, or blocking it from, the food chain.
Some scientists have suggested that the lack of thiamine may be the result of another problem, such as botulism, and that it’s the botulism that’s actually killing the birds. But Farr said that seems unlikely.
“If they had another major underlying problem like botulism they wouldn’t recover so quickly with a shot,” she said.
It was Sea Grant’s Zhuikov who may have closed the loop on what’s causing the problem in gulls based on research she has seen about Vitamin B in fish. Indeed, research has confirmed that some Great Lakes fish — namely alewives and smelt, both invasive species that swam into the Great Lakes a century ago — are lacking thiamine. It stands that birds that eat those fish regularly would then not get enough thiamine in their diets, Zhuikov noted.
According to that research, both smelt and alewives contain thiaminase — an enzyme that destroys thiamine and causes deficiencies in bigger fish that eat smelt and alewives. It was first noted decades ago by mink farmers who observed that, when mink were fed raw smelt, the mink didn’t reproduce.
It took longer for biologists to realize something called “early mortality syndrome” in lake trout and other salmonids was caused by a thiamine deficiency resulting from eating smelt and alewives. It eventually became clear that fish that fed heavily on smelt and alewives produced larvae that didn’t survive very well.
Research by the U.S. Geological Survey published in the journal Fish and Shellfish Immunology in April found a very specific link between thiaminase and vitamin B1 deficiency in bigger fish including salmon, steelhead trout, brown trout and lake trout. The fish also suffered immune system problems. The symptoms of early mortality syndrome include loss of equilibrium, swimming in a spiral pattern, lethargy, hyper-excitability, hemorrhaging and death.
“Vitamin B1, or thiamine, is an essential nutrient that animals must obtain through their diet,” said Chris Ottinger, a USGS immunologist and lead author of the study, in releasing the report. “The lack of B1 leads to early mortality syndrome as well as the newly reported immune dysfunctions that may be perpetuating infectious diseases in this fish community.”
It’s been speculated that an abundance of smelt and alewives likely slowed efforts to restore native lake trout populations in some of the Great Lakes. In Lake Superior, smelt numbers generally have declined in the past 50 years while native herring, which don’t have thiaminase, are rebounding, as are lake trout populations.
“This seems to close the loop a little. It’s as good an explanation as we’ve seen on why Vitamin B would be such an issue for gulls,” Farr said. “It doesn’t explain why only some of the birds are having a problem. Maybe the other gulls are getting most of their diet from McDonald’s french fries and not smelt.”