Story by Elaine Caton Blackfoot Challenge Swan Program Coordinator
The Blackfoot Challenge recently learned of the deaths of four trumpeter swan cygnets born to Blackfoot swan 3A6 in Sheridan, Wyoming. 3A6 was released in the Blackfoot in 2016 and nested in the Sheridan area this year. The cygnets were determined to have died of the Highly Pathogenic Avian Influenza (HPAI), or avian flu.
While the current strain of avian flu is highly deadly to domestic poultry, it appears to be much less lethal to most wild birds. However, waterfowl (birds like ducks, geese, swans, coots, grebes, etc.), some raptor species (especially red-tailed hawks, bald eagles and great horned owls), and scavengers like ravens, crows and magpies are more susceptible and experiencing higher mortalities. These species might have higher exposure because of their habits (flocking together, and/or eating infected birds), or they might be more likely for physiological reasons to succumb to the disease, or both.
As of November 10, 188 cases of Avian Influenza have been reported in wild birds in Montana since the start of 2022, out of 7,572 cases nationally (according to the USDA APHIS website). Most of those cases have been in ducks (88), geese (25), owls (23), and hawks (18). There have been two known cases in trumpeter swans in Montana: one in Ravalli County and one in Lake County. The majority of cases detected in ducks have been from hunters submitting birds for testing. Flu cases in waterfowl and other birds are likely to increase during migration and winter, when large flocks congregate. Because the virus causes neurological damage, infected birds likely become easy prey for raptors and other predators, who are then likely to contract it themselves.
Avian flu has also been detected in a few mammals (including bears, foxes, and skunks), thought to have contracted it by scavenging dead birds. It is rare for humans to contract the current avian flu strain, and there has been only one confirmed case in the United States, from contact with contaminated poultry.
People are often concerned about bird feeders facilitating the spread of flu among songbirds and even to humans. However, infection among
songbirds and other species that might frequent feeders appears to be quite low (less than 2% of all cases in wild birds). This could change as more testing is done on wild birds, or if the disease evolves to become more contagious and/or lethal. However, at this time there appears to be little effect on the chickadees, nuthatches, grosbeaks, juncos and other birds we are likely to see outside our windows in the winter in the Blackfoot.
This outbreak of a lethal disease strain highlights the vulnerability of small populations of any species to unforeseen events that might impact their survival. Although we have met the goals of the original restoration plan for trumpeter swans in the Blackfoot, the relatively small number of swans that summer and breed in our watershed means the population here is easily impacted by events like disease outbreaks, unusually severe weather, and loss of habitat. Although we can’t control the weather or wildlife diseases, we are fortunate to have so many private and public landowners stewarding the wetlands that swans and so many other species depend on in our watershed.
If you see wild birds acting unusually lethargic or uncoordinated, or find a dead raptor or scavenger or a number of dead waterfowl, please contact your local Montana Fish, Wildlife, and Parks office or the Montana State Wildlife Health Lab at 406-577-7882.