SAN JOAQUIN VALLEY, Calif. — After this year’s historic rains filled the San Joaquin Valley’s Tulare Basin for the first time in decades, migratory birds began flocking to the newly waterlogged habitat. That stagnant water has now become a breeding ground for the bacterium Clostridium botulinum, which causes paralysis and death in infected birds.

Veterinarians like Dr. Jamie Sherman of the Oiled Wildlife Care Network out of UC Davis have been stationed near the lake for weeks, trying to nurse ailing birds back to health. Those avian patients are collected from the lake's surface by the California Department of Fish and Wildlife's experts, like biologist Evan King. So far, King has collected about 3,500 birds in less than two months, and Sherman has taken in 800 of those for treatment.

Birds are typically infected with Avian botulism after ingesting infected decaying organic matter or invertebrates, according to the United States Geological Survey. The toxin interferes with nerve transmission to muscles and eventually leads to progressive muscle weakness, difficulty flying and paralysis of the muscles required to breathe. Many waterfowl killed by botulism drown because they become too weak to hold their heads above water. 

According to Sherman, many birds recuperate fully after four to five days of treatment, which largely involves the injection of hydrating fluids and the tube-feeding of nutrient-dense foods. King's efforts to slow the spread of the disease by removing dead specimen have so far proven successful, as he has reported fewer infected birds on his most recent trips out on the lake.