The California Department of Fish and Wildlife (CDFW) is closely monitoring the population of band-tailed pigeons for mortality this winter. Band-tailed pigeons are California’s only native pigeon. They spend their winter from central to Southern California primarily inhabiting oak woodland and conifer forests. In late winter into early spring, band-tailed pigeons will migrate north into northern California, Oregon, Washington and British Columbia. Band-tailed pigeons are a different species than rock pigeons (also called city, urban or barn pigeons), which were introduced into North America from Europe.
Large flocks of band-tailed pigeons, sometimes up to 200 birds, have been observed in numerous coastal locations from the San Francisco Bay Area south into Santa Barbara County and in the San Bernardino Mountains. Increased mortality has been reported in several of these areas since mid-December. CDFW’s Wildlife Investigations Laboratory has evaluated carcasses from these locations and determined the cause of mortality to be Avian Trichomonosis.
Avian Trichomonosis is a disease caused by a single-celled microscopic protozoan parasite, typically Trichomonas gallinae, which only infects birds. The parasite lives in the mouth and throat of infected birds, causing caseous (“cheese-like”) lesions in the birds’ mouth or esophagus. The lesions eventually block the passage of food, causing the bird to become weak and emaciated. Infected birds die from starvation or suffocation if the lesions block the airway. Non-native rock pigeons are thought to be the source of infection for native bird species.
The CDFW’s Wildlife Investigations Lab is asking residents to be on the lookout for band-tailed pigeons this winter and to report any sick or dead pigeons. This information helps CDFW determine how many pigeons die during these mortality events and consequently, how these events may impact the overall population. Mortality can be reported using the following link: https://www.wildlife.ca.gov/Conservation/Laboratories/Wildlife-Investigations/Monitoring/Mortality-Report or by phone at (916) 358-2790.
If sick birds are observed, please contact a local wildlife rehabilitation center for advice. The list of CDFW licensed centers can be found at http://www.dfg.ca.gov/wildlife/WIL/rehab/facilities.html.
Additionally, residents can help reduce transmission of the disease by removing artificial sources of food and water (bird baths and fountains). Bird feeders and artificial water sources may increase disease transmission between individual band-tailed pigeons, and possibly other bird species, because it brings the birds into closer contact than is normal.