Bird Die-Off Update
Contact: Steve Yancho, 231-326-5134
Biologists at Sleeping Bear Dunes National Lakeshore were recently informed by lab specialists at the Michigan Department of Natural Resource Wildlife Disease Laboratory that Type E Botulism remains the culprit in the deaths of an assortment of bird species along the Lake Michigan shoreline. According to Lakeshore Biologist Ken Hyde, the outbreak began this summer and continues to primarily impact fish-eating birds. Hyde reported that “We have recently observed a significant die-off of Horned Grebes, Mergansers, and Common Loons in addition to the more commonly seen Cormorants and Gulls. Estimates of the total number of birds lost to Type E Botulism since August, just along the beaches of the Lakeshore, are approaching 2,600 birds.”
Early indications of what may have caused such a significant release of Type E Botulism into the ecosystem are not clear. Type E Botulism-caused bird die-offs were first reported on Lake Michigan in 1963. Hyde’s research into the problem has shown that these die-offs have become common in shoreline locations across the Great Lakes and that the outbreaks are often related to an upwelling of lake-bottom sediments containing the Type E Botulism. Hyde postulated that “Sediments that contain the bacteria are being filtered by non-native Zebra Mussels, thus concentrating the Botulism in the mussels. The mussels are then eaten by non-native Round Gobies, which in turn are consumed by the affected birds.” Hyde went on to say that “The gobies are recent invaders that are steadily increasing in number throughout the Great Lakes and are becoming a significant food source for many fish-eating birds. These fish can concentrate PCBs and, apparently, botulism from the Zebra Mussels as well.”
According to Hyde, there is no indication that this bird die-off represents any type of human health threat. It is unknown, however, whether there is a risk to dogs that feed on the dead birds. When asked about this concern Superintendent Dusty Shultz reminded visitors that “All dogs must be kept on a leash when in the park, and this is especially important when visiting beaches that are open to dogs. This not only protects other visitors and wildlife, but protects the dogs as well.”
Although park visitors and neighbors continue to express concern about the dead birds on the beaches, it appears that the carcasses are more of an aesthetic concern than a health risk to wildlife or humans. Biologist Hyde noted that, “Because of the environmental pathway the botulism is taking, it appears that direct actions such as burial or removal will have little chance of stopping or even slowing outbreaks such as this one.” Superintendent Shultz agreed, saying, “The Lakeshore appreciates all of the interest in this issue and the many offers of help. There is a great sense of loss each time a Common Loon or other bird is found and since there are very few management options available, there is hope that nature will soon resolve this very difficult situation. Unfortunately, with two rapidly increasing non-native species as the suspected delivery mechanism, this is a problem that may be with us on a reoccurring basis.”
Did You Know?
In the US, invasive species are the second biggest threat to native ecosystems after habitat loss. They reduce diversity, alter disturbance regimes, and have cascading effects on food webs, costing upwards of $140 Billion per year. More...