Avian botulism has been a problem at some units of the National Park System located along the Great Lakes. Biologists working to better understand the spread of the disease are turning to loons to help with their research.
U.S. Geological Survey biologists recently attached satellite transmitters to the legs of 10 common loons so they can follow their migratory movements and feeding patterns.
In recent years, tens of thousands of birds have perished from botulism that is erupting in the lakes, and which some scientists believe is partly a result of climate change. Species impacted include the common loon, Minnesota’s state bird; mergansers, which summer and winter on portions of the lakes; Double-crested cormorants, which migrate through the region and summer on the lakes; and even the piping plover, an endangered shorebird that summers on portions of the lakes.
“This study will also help managers better understand how loons fare as they head to their wintering grounds along the Gulf of Mexico and Atlantic coasts,” said USGS scientist Kevin Kenow, of the Upper Midwest Environmental Sciences Center in La Cross, Wisconsin. “Right now, little is known about habitat use along their entire migratory routes.”
Common loons, a large black-and-white waterbird with lyrical calls, are an iconic species in the Great Lakes states, where the USGS says they are most abundant. Unlike most birds that have hollow bones, "loon bones are dense, helping them to dive to depths of some 250 feet in their search for food."
Along with the 10 satellite transmitter-marked loons, about 70 other loons will be fitted with geolocator tags that will record daily location, temperature, light levels and water-pressure data that will log the foraging depths of these diving birds.
“This information will help shed light on how avian botulism may work in the food web on the Great Lakes,” said Mr. Kenow, the leader of the migration project.
Botulism, which has caused more than 80,000 bird deaths on the Great Lakes since 1999, causes paralysis and death of vertebrates who ingest neurotoxin produced by the botulism bacterium, according to a USGS release.
The USGS study on avian botulism on the Great Lakes, funded by the Great Lakes Restoration Initiative, is designed to "examine the pathways by which fish and birds acquire botulinum toxin from Great Lakes food webs and determine how avian botulism outbreaks are related to environmental variables such as water quality and food web structure," a USGS release said. "Avian botulism outbreaks have resulted in periodic and often huge die-offs of fish-eating birds since at least the 1960s, but outbreaks have become more common and widespread since 1999, particularly in Lakes Michigan and Erie."
“Understanding feeding patterns and exposure routes of waterbird species at high risk for botulism die-offs, such as the common loon, is central to understanding how botulism exposure happens in the aquatic food chains in the Great Lakes and to eventually identifying what drives botulism outbreaks,” said Mr. Kenow, “Only then, can we help provide tools to prevent or lessen such outbreaks.”
Movement of loons from previous studies carrying satellite transmitters can be followed online at the USGS UMESC website. Loon movements from the current study will be available later this summer.