Irruption & Salmonellosis Outbreak
California is currently experiencing a Salmonellosis (“Salmonella”) Outbreak. Salmonellosis is a fatal bacterial infection that rapidly spreads through populations of wild birds via feces-contaminated food and water. Most often, Salmonellosis Outbreaks originate where birds flock to feeders or baths. Infected individuals will appear lethargic, puffed/fluff-up, with eyes partially closed; on occasion eyes may also appear swollen, red, or irritated.
Pine Siskins – tiny, heavily streaked, yellow-accented finches – are especially susceptible to Salmonellosis. Pine Siskins occur naturally in small populations across Sonoma County; however, this winter we are seeing huge numbers migrating in. This mass-migration is referred to as an “Irruption Year”, a natural phenomenon driven by fluctuations of available resource. This winter, there is a shortage of tree seeds across Canada’s boreal forest (the normal wintering grounds for Pine Siskins), causing siskins to ‘irrupt’ south in search of food. According to a recent article from The National Audubon Society, this winter’s irruption is one of the largest in recorded history. In fact, siskins have even been reported migrating at night – a very odd spectacle for a diurnal species.
Not only are Pine Siskins especially susceptible to the disease, they are also carriers of Salmonellosis, spreading it throughout the environment. Therefore, we often see Salmonellosis Outbreaks correlated with irruption years, which is what is occurring now. If the disease persists in the environment for long enough, it will eventually spread from Pine Siskins to goldfinches, other finch species, and beyond, penetrating deep into the avian community.
To date, The Bird Rescue Center is being hit hard by the Salmonellosis Outbreak. Since mid-November, we have been fielding dozens of calls every day about sick Pine Siskins and Salmonellosis. Our hospital has received more than double our average number of intakes for this time of year, with Pine Siskins serving as over 40% of all intakes. Unfortunately, we are now seeing the disease in American Goldfinches, Lesser Goldfinches, House Finches, and Purple Finches. As we enter into the peak of the Salmonellosis Outbreak, some days Salmonellosis is the entirety of our new caseloads, with well over two dozen cases a day.