A large outbreak of a disease caused by the Salmonella bacteria is rapidly spreading among finches in Northern California. The disease kills most infected birds between 24 and 48 hours after infection, and spreads quickly when birds gather in large groups. 

Pine Siskins are the primary bird being affected, but Lesser Goldfinches and American Goldfinches are affected in smaller numbers. 

According to California Department of Fish and Wildlife Senior Environmental Scientist, Krysta Rogers, the disease, Salmonellosis, is caused by a variant of the Salmonella bacteria called Salmonella Typhimurium. Outbreaks occur periodically in Pine Siskins, but the current outbreak is particularly rampant.

“It’s rare to have a massive outbreak like this one,”explained Alison Hermance, Director of Communications at WildCare in San Rafael.

“By intake numbers in the [WildCare] Wildlife Hospital, the last larger outbreak -76 birds admitted- was in 2015. Before that, it was 2008. Most years see fewer than a dozen Pine Siskins admitted with salmonellosis symptoms. Since December we have admitted 136 sick Pine Siskins,” she said.

Locally, Katie Miller, the hospital manager at The Bird Rescue Center of Sonoma County, explained that “this is by far the worst outbreak The Bird Rescue Center has ever witnessed… we have admitted over 250 patients in 2021 – more than double our average – and over 40% of these admits are due to the current Salmonella outbreak. Generally, we get at least one new salmonella case everyday, though some days we intake more than 5 affected individuals. ”

On a larger scale, Rogers explained that between Dec. 20 and Feb. 8, there have been 1,044 mortality reports statewide, and “the highest number of reports are from Sonoma, Marin, Santa Clara, San Mateo, Contra Costa, and Santa Cruz counties,” respectively. 

She said the absolute number of cases is likely much higher, as figures and estimates are based on community members reporting sick or dead birds, and data is skewed towards areas that have higher human populations.

Rogers and Miller both said that outbreaks occur due to the changing migratory patterns of Pine Siskins, which migrate based on food availability and not solely on geographic location.

“The hypothesis behind the severity of the current 2020-2021 outbreak is due to the massive pine siskin ‘irruption’ – mass migration of pine siskins south from Canada’s Boreal forest in search of better food supplies. According to a recent article from The National Audubon Society, this winter’s irruption is one of the largest in recorded history,” Miller stated in an email.

The article, published in Oct. 2020, explained that the birds migrate “southward in years when there is a shortage of food in their home range. This year, a meager supply of conifer seeds across Canada’s boreal forest has caused the birds to push south in mind-boggling numbers.”

While the vast majority of cases occur within the Pine Siskin population, the Bird Rescue Center is also seeing cases of Salmonellosis in Purple Finches and House Finches, which is unusual compared to previous years.

The Sonoma County Wildlife Rescue, among other wildlife rescue organizations, are telling community members to remove bird feeders and bird baths, to prevent large gatherings of birds. Salmonellosis spreads quickly and easily when large groups of birds gather in concentrated areas. 

Hermance also explained that it’s important that individuals regularly clean their feeders, bird baths, and birdhouses.  

“Outbreaks like this happen because birdfeeders aren’t kept clean. If you are feeding birds, you have a responsibility to make sure your feeder is clean and disease-free. Washing and bleaching with a ten percent bleach solution (nine parts water to one part bleach) weekly will prevent diseases like Salmonellosis from killing our songbirds,” she said. 

Miller warned that pets and children are at risk of infection if they touch or come in contact with dead or infected birds, as well as contaminated feeders and bird baths, and stressed that “once it is safe to put our feeders and baths back up, it is imperative they be cleaned on a weekly basis, year round.” The recommendation is to refrain from putting out feeders and baths until late spring, when Pine Siskins go back north. 

Juan Mendoza, a Santa Rosa native who works at Absolute Homes and Gardens in Sebastopol, had been occasionally filling his feeders when he started to notice sick birds in his yard. 

“Around December, I went and got a little bag [of food], almost like a Christmas present to the wild birds, and I did two of my feeders instead of 10 of my feeders… then I started noticing extra shabby little birds… they seemed… quieter, and… they were fluffed up… and they just didn’t look right,” he explained. When he found a dead bird he “completely stopped feeding and I started washing my bird baths and wash[ing] the bird feeders.” 

As a person who owned pet parakeets as a child and regularly rescues birds, Mendoza explained that the best way to help wildlife is to replace refillable feeders with natural plants. 

“I wish that people will plant more native plants and stop feeding them. I know it’s very hard, it was very hard for me, but you just have to do it. Take the bird feeders down and just hope for the best that [the outbreak] is going to go away and they’re gonna survive, you know it’s just sad,” he said. 

Slowing the spread of this disease is just one environmental problem that humans can help reduce the impact it has on local wildlife. Climate change and protecting natural spaces is important to help keep local wildlife healthy. The director for the Naturalist Program at Sonoma State University, Suzanne DeCoursey, explained that many pathogens found in animals and plants are exacerbated by problems like climate change and the loss of natural habitats due to human activities. 

“We often think of climate change as mainly affecting things like temperature and sea level, but it can also affect disease impact and range, among both human and non-human species,” she said. 

Similarly, Susan Stanton, a citizen in Oakland and avid bird watcher, explained that the “loss of habitat and climate change” affects all wildlife, and is another environmental issue that affects birds and nature in general.

If dead or sick birds are seen or found in the area, individuals are encouraged to report those to wildlife centers in their area. Do not touch or handle any dead or sick birds as the infection can be transmittable to humans. If it is necessary, though, wear protective gloves and thoroughly wash hands afterwards. 

Sick birds will generally appear weak and “lethargic, puffed or fluffed up, with partially closed or ‘sunken’ eyes. On the rare occasions, eyes may alternately appear swollen, red, or irritated,” Miller said.

The California Department of Fish and Wildlife has a full list of centers on their website https://wildlife.ca.gov/Conservation/Laboratories/Wildlife-Investigations/Rehab/Facilities, listed by county. 

For Sonoma County residents, The Bird Rescue Center should be contacted at (707)523-2473 as soon as a sick or dead bird is found.