February 23, 2023 – Since early February, the California Department of Fish and Wildlife (CDFW) and many wildlife rehabilitation centers have received increased reports of sick and dead band-tailed pigeons from residents. Most reports have come from locations along California’s Central Coast, the San Francisco Bay Area and foothill communities in the Sierra Nevada Mountains.
CDFW’s Wildlife Health Laboratory has evaluated birds from several locations and determined the cause of death to be avian trichomonosis, a disease caused by a protozoan parasite, typically Trichomonas gallinae. Statewide, its estimated that roughly 200-300 band-tailed pigeons may have died of this infection so far this winter.
“Avian trichomonosis outbreaks occur periodically in band-tailed pigeons during some winters in California,” said CDFW Senior Environmental Scientist Krysta Rogers, an avian disease specialist. “Historically, larger outbreaks generally have been associated with drier conditions because the pigeons may be more likely to share a reduced number of water sources and the parasite can spread more rapidly among birds in the flock.”
Band-tailed pigeons are native to California and may be unfamiliar to some residents given their mostly secretive and highly nomadic lifestyle. During winter, nearly the entire Pacific Coast population of band-tailed pigeons congregates in areas of Central to Southern California, sometimes forming relatively large flocks and seeking out acorns, their preferred food in winter.
The parasite that causes avian trichomonosis is primarily spread in water sources such as bird baths, fountains, and horse or cattle troughs where the parasite may become more concentrated. Once infected, caseous lesions (“cheese-like”) may develop in the bird’s mouth or throat leading to starvation or suffocation.
Sick birds may appear weak, swallow repeatedly, have labored breathing, and may sit for prolonged periods. Severely affected birds may develop neurological signs such as lack of coordination or twisting of the head or neck. Band-tailed pigeons are especially susceptible to avian trichomonosis. Other bird species also may be susceptible when sharing water sources as are avian predators that may feed on infected birds.
Residents can help reduce disease transmission among birds by removing bird feeders and bird baths and emptying fountains while the pigeons are in their area. Observations of sick and dead pigeons may be reported to CDFW using the mortality reporting form. These reports are important to help document when and where birds may be impacted.
If there is a need to dispose of a dead bird, CDFW recommends wearing disposable gloves to collect the remains into a plastic bag, which may then be placed in the regular trash collection. Afterward, wash hands with soap and water. For guidance on orphaned, injured or sick live-wild birds, please contact your nearest wildlife rehabilitation center before collecting the animal.