Over the past two decades, DDPHE staff have observed dead and dying birds in the City’s lakes. The observations occur in the hottest months of the year, typically between late June and September. Two possible causes for the dead and dying birds have been identified: Avian botulism and West Nile Virus.
Avian botulism affects waterfowl and shorebirds that ingest a toxin which is commonly found in sediment at the bottom of lakes. Birds suspected of having avian botulism often have trouble holding their necks and heads up and may also appear to struggle to swim across the water. Unfortunately, death by drowning is often the end result.
City staff routinely monitor for potential signs of avian botulism during warmer weather and respond by removing bird carcasses and working with rescue organizations to help sick birds as quickly as possible. Sick birds stand a good chance of surviving when promptly treated by local bird rehabilitators. Leaving infected carcasses in and around the waterbody increases the spread of the disease. It's very important that all carcasses, birds and others, be removed.
For more information, visit USGS – Avian Botulism.
West Nile virus is a disease transmitted by mosquitoes. Mosquitoes become infected after biting an infected bird and then may pass the virus on to other birds, humans or animals. Mosquitoes carry the highest amounts of virus in late August and September until the weather cools and mosquitoes die off. To most, West Nile virus symptoms in birds appear to be similar to those of avian botulism.
For more information, go to CDC’s West Nile Virus web page.
Please contact DDPHE by calling 311 if you see multiple sick or dead birds in your neighborhood.