The Wildlife Investigations Lab is monitoring pine siskins for mortality this winter. Pine siskins are a type of finch that are mostly brown in color with a bright yellow wing stripe that live in forested areas in California primarily during the winter. Pine siskins are an irruptive migrant, meaning they can be found in high densities in certain areas in some years, but often absent the next. This migration pattern is likely determined by food availability and weather conditions.
This winter pine siskins have been reported in numerous areas throughout California with larger concentrations occurring along the central and south coasts as well as around Redding, in northern California. Increased mortality of pine siskins has been reported in several of these areas since mid-December. The Wildlife Investigations Lab has evaluated carcasses from these locations and determined the cause of mortality to be Salmonellosis, a disease caused by Salmonella bacteria.
Salmonellosis occurs periodically in some years in pine siskins throughout their range. Previous outbreaks in California occurred during the winter of 2012-13 and in 2015. Birds become infected with Salmonella bacteria when they ingest food, water, or come into contact with objects (e.g. bird feeders, perches, soil) contaminated with feces from infected birds. Sick birds often appear weak, have labored breathing, and may sit for prolonged periods of time with fluffed or ruffled feathers. Salmonellosis is highly fatal in pine siskin, with most birds dying within 24 hours after infection.
Salmonellosis in pine siskins is almost exclusively reported from locations with bird feeders that attract increased numbers of birds. Residents can help reduce transmission of the disease by removing artificial sources of food and water (bird baths and fountains) as these may increase disease transmission between individual pine siskin, and possibly other bird species, because they bring birds into closer contact than would occur normally.
Dead birds may be reported to the Wildlife Investigations Lab to help determine locations and numbers of birds affected during this Salmonellosis outbreak.
If sick birds are observed, please contact a local licensed wildlife rehabilitation center for advice.