Dead birds and squirrels are often the first indicator that West Nile virus exists in an area.

Certain species of birds are very susceptible to West Nile virus and will die quickly after infection, while others can live with the virus. Information on the species and location of infected birds is used to make calculated decisions on mosquito control.

When the District finds West Nile virus in a dead bird, we then trap mosquitoes in the area where the bird was collected to see if they’re infected with the virus. The laboratory typically sets 20 traps in a 1/2 mile radius around the location where the bird was found. The traps are collected the following morning and the mosquitoes are tested for West Nile virus.

For more information about West Nile virus, visit the California West Nile virus website.

The District collects and tests suitable birds of the following groups:  corvids, finches, sparrows, owls, and hawks.

You can submit a dead bird report to the California Department of Public Health (CDPH) year-round using their online form, or you can call and report a dead bird to the WNV Call Center from April to October. The phone number is:

1-877-968-2473 (1-877-WNV-BIRD)

Other diseases that affect wild birds

Diseases besides West Nile virus can affect wild birds. Taking down bird feeders can help keep wild birds healthier. To learn more about bird feeders, visit CDFW's page.

To report an unusual number of sick/dead birds, file a report on California Department of Fish and Wildlife's website or call 866-922-BIRD (2473)

Salmonellosis and pine siskins

Pine siskins, small finch species commonly seen at bird feeders, are more likely than other birds to get sick with Salmonellosis, and may die from this infection in large numbers. You can learn more about previous outbreaks of Salmonellosis in pine siskins from California Department of Fish and Wildlife's posts about the 2016 outbreak and 2020-2021 outbreak. It’s also important to remember that Salmonellosis in birds is caused by the same bacteria that can cause ‘food poisoning’ in humans, so remember to pick up dead birds with gloves or an inverted plastic bag, and always wash your hands after.

Avian influenza, wild birds, and backyard flocks

Avian influenza is a type of novel influenza virus. It refers to the disease found in birds that is caused by infection with avian (bird) influenza (flu) Type A viruses. These viruses naturally spread among wild aquatic birds worldwide and can infect domestic poultry and other bird and animal species. Avian flu viruses do not normally infect humans; however, sporadic human infections with avian flu viruses have occurred. In early 2022, highly pathogenic avian influenza (HPAI) started to affect wild birds in the United States. This disease has been found in California in wild birds, as well as in commerical and backyard flocks. To learn more about HPAI, visit one of the following sites:

• California Department of Fish and Wildlife current news page
• California Department of Food and Agriculture page
• CDC Avian Influenza/Bird Flu page
• USDA APHIS Avian Influenza page

Page last reviewed: December 30, 2022