Thousands of dead pigeons have been discovered since mid-December, and biologists think they are dying from a parasite that effects only birds, and seems to be hitting the band-tailed pigeon — the only native pigeon in California — especially hard.
Band-tailed pigeons are large, stocky birds with small heads, long and rounded tails, and yellow bills and feet. Their heads and breasts are purplish gray and they have a white crescent on the backs of their necks.
They spend the winters in Central and Southern California near oak trees and coniferous forests, often in large flocks. When the weather warms, they migrate north into Northern California and the Pacific Northwest.
Since December, state wildlife scientists have been investigating the large-scale deaths of the birds, which appear to be perishing from a disease called avian trichomonosis.
Caused by a protozoan parasite, the disease only infects birds. It lives in the bird’s mouth and throat, producing lesions that block the passage of food and cause the bird to starve to death or suffocate.
It’s unclear what is causing the parasite, although non-native rock pigeons may be the source of the infection for native bird species, the CDFW reported last month.
Krysta Rogers, a CDFW environmental scientist, said that the majority of the dead pigeons have turned up in Los Olivos, Santa Ynez and Solvang, with a few cases found in Carpinteria and Santa Barbara.
Rogers didn’t have an exact number because scientists are still conducting research, but she said the deaths are in “the low thousands” for the county. Those figures are just based on reports from people who discovered the dead birds, however, and more may have perished without having been reported.
A large number of dead birds also have been reported in Santa Clara County, Rogers said, adding that the deaths seem to be occurring with more frequency in recent years.
“That is concerning because we know their population has been declining, but we don’t really know what kind of effect it will have,” she said.
The department has been receiving reports from the U.S. Forest Service, as well as workers in licensed animal rehabilitation centers.
Rogers said “the main driver for where the pigeons are is food,” and that the locations where dead pigeons have been found are often near oak trees, whose acorns are a main source of their food.
“We’re still receiving a lot of inquiries from the public, and we’re encouraging them to report sick or dead pigeons so we can come up with a more accurate number,” she said.
Pigeons are primarily affected by the disease, although a rare raptor that has eaten a pigeon might be found dead, she said.
“There may be mild concerns with backyard chickens,” she said, adding that owners should keep feed and water covered from other types of birds.
There is no risk of transmission to humans or to other animals, she said.
Click here to make an online report of sick or dead pigeons, or call 916.358.2790.
Residents also can help reduce the transmission of the disease by removing artificial sources of food and water, like birdbaths 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, the department said.