A disease caused by salmonella bacteria that spread through bird feeders and birdbaths is killing songbirds across California, the California Department of Fish & Wildlife warned this week.
Salmonellosis is striking down mostly pine siskins, a species of finch that migrates from Canada. Smaller numbers of lesser goldfinches and American goldfinches have also been stricken with the disease. Most sightings of these sick or dead birds have been in the Bay Area, Central Coast and Sierra Nevada.
Pine siskin are an “irruptive” species, says, Krysta Rogers, a senior environmental scientist at CDFW, because their migration patterns are sporadic and heavily dictated by where they can find food.
She said when birds move to this type of alternative food source, it's often due to "high reproductive success."
"So there's lots of new birds in the population and then maybe some depleted food resources in their breeding areas," Rogers said. "And so they move to find food."
And often, they'll start using bird feeders, which is where the trouble starts. Intestinal bacteria spreads through feces, so areas where birds congregate are a problem. When the birds poop in platform bird feeders or in a birdbath, Rogers said, "the next bird that comes along and either takes a drink out of that water or eats seeds that might be contaminated with the feces can get infected that way.”
Rogers says salmonella bacteria can live for days or even months, so no amount of cleaning will be able to keep pace with the spread.
The safest thing people can do is take down the feeders, she says, at least until the birds clear out, which usually happens in March and April.
Until then, keep an eye out for finches gathering around your feeders.