Efforts Intensify To Assist Avian Botulism-Affected Birds At Tulare Lake

Oiled Wildlife Care Network Responding to Help Birds

Ibises rest besides plates of food and water in an outdoor enclosed wildlife care facility
White-faced ibises collected from Tulare Lake following an avian botulism event rest in outdoor enclosures in September 2023. (OWCN, UC Davis)

The California Department of Fish and Wildlife (CDFW), joined by state, federal and non-governmental organization partners, has intensified its response to help birds affected by avian botulism at Tulare Lake. The agency is contracting with the expert Oiled Wildlife Care Network (OWCN), a program of the UC Davis School of Veterinary Medicine, to provide emergency veterinary care.

Avian botulism is caused by a toxin-producing bacteria that occurs naturally in bodies of water like Tulare Lake.

Tulare Lake, once the largest freshwater lake west of the Mississippi River, reemerged from the pastures and agricultural fields in the southern San Joaquin Valley this year because of California’s extraordinarily wet winter and spring and is attracting water birds of all sorts. The lake is expected to attract millions of waterfowl, shorebirds and other bird species as fall migrations get underway in earnest.

Person wearing UC Davis Veterinary Shirts examines a bird impacted by botulism wearing purple medical gloves
A wildlife care responder from the Oiled Wildlife Care Network, a program of the UC Davis School of Medicine, examines a black-necked stilt following an avian botulism outbreak at Tulare Lake in California in September 2023. (OWCN, UC Davis)

1,678 birds collected since August

CDFW crews are patrolling the lake daily using airboats to help collect affected birds and monitoring for dead birds. The overall number of birds being collected has increased each week. There are a total of 1,678 birds collected since early August. Last week responders collected 530 birds and the daily average is between 50 and 100 birds recovered. The OWCN reports as of Thurs., Sept. 7, 169 live birds have been admitted for intensive care at its facilities.

Sixteen birds have been submitted to CDFW’s Wildlife Health Laboratory for postmortem examination and subsequent testing. Low pathogenic avian influenza viruses were detected in three birds. Highly pathogenic avian influenza has not been detected in the birds tested. Avian botulism type C was confirmed in five of eight birds tested for the toxin, additional testing is ongoing.

Care facilities

The OWCN has constructed a temporary facility that once fully established, will be able to care for up to 250 avian botulism-affected birds at a time on site. The care of these birds will be provided by veterinarians and wildlife rehabilitators from UC Davis and OWCN’s 45 member organizations throughout the state.

The onsite rehabilitation facility is located at the Kern National Wildlife Refuge. The facility contains a house retrofitted to serve as an animal hospital and substantial outdoor housing using military grade tents, providing shade, water and a safe environment to help treat the sick birds.

Two wildlife care responders treat a bird, partially covered by a cloth, for botulism
Danene Birtell (OWCN and UC Davis) and Jeanette Bates (International Bird Rescue) perform an intake exam on an avian botulism patient. (OWCN, UC Davis)

“Birds that have been collected are stabilized and cared for onsite with more sensitive species being sent to Stanislaus Wildlife Care and International Bird Rescue,” said Michael Ziccardi, director of the OWCN and executive director of the One Health Institute at UC Davis. “Of those, 29 have made a remarkable recovery and were released on the Kern National Wildlife Refuge. OWCN is proud to be able to partner with CDFW in this effort to protect the welfare and conservation of California's wildlife.”

An additional 125 birds at a time will be able to receive care at off-site facilities managed by several OWCN member organizations. These currently include the International Bird Rescue and Stanislaus Wildlife Care Center but may be expanded to additional organizations as needed. The running total numbers of impacted birds will be updated at least every 48 hours and can be viewed at https://owcn.vetmed.ucdavis.edu.

A response team has been assembled consisting of CDFW, OWCN, the California Office of Emergency Services, the U.S. Fish and Wildlife Service, the California Natural Resources Agency, the Federal Emergency Management Agency, California Waterfowl and others. 

Mortality reporting

Residents in the Tulare Lake Basin are encouraged to report incidents of wildlife mortality to CDFW using the web-based mortality reporting form or by contacting CDFW’s Central Region office. These reports are important and help biologists monitor conditions for wildlife in and around the lake.

Avian botulism type C outbreaks in wild birds are typically not associated with human botulism, which is caused by other botulinum toxin types. Wild birds, especially waterfowl and shorebirds, are most frequently affected by botulinum toxin type C. An information sheet addressing frequently asked questions concerning avian botulism is available on CDFW’s website.

CDFW wildlife rescue responder holds duck during botulism outbreak at Tulare Lake
CDFW, Oiled Wildlife Care Network and partners have intensified rescue and response efforts for birds affected by avian botulism at Tulare Lake. As of Sept 7, 2023, the UC Davis-managed OWCN reports that 169 live birds have been admitted for intensive care at its member facilities.(CDFW)

About Oiled Wildlife Care Network 

The Oiled Wildlife Care Network is a collaborative effort among member organizations, dedicated to providing the best achievable capture and care for oiled wildlife in California. Established to respond to oil spills, the OWCN's mission has expanded to include other wildlife crises, such as the avian botulism event addressed in this release. The OWCN's commitment to wildlife rehabilitation and conservation remains unwavering. 

This news release is reposted from the CDFW release issued Sept. 8, 2023.

Media Resources

  • Steve Gonzalez, CDFW Communications, (916) 804-1714, Steve.Gonzalez@wildlife.ca.gov
  • Kat Kerlin, UC Davis News and Media Relations, 530-750-9195, kekerlin@ucdavis.edu 

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Environment Human & Animal Health One Health