An ongoing outbreak of botulism, a bacterial illness that causes muscle paralysis, has killed more than 94,000 birds at Tule Lake National Wildlife Refuge in Northern California, the worst such outbreak at the lake ever recorded, according to federal scientists. Affected birds often cannot control their muscles and often suffocate in the water, said biologist and ornithologist Teresa Wicks, with Bird Alliance of Oregon, who works in the area. “It’s a very traumatic thing to see,” Wicks said. Though local in scale, the outbreak and catastrophic die-off are tied to global problems including declining wetlands, increasing demand for limited water resources, hydrological diversions, and a warming climate. These kinds of outbreaks can happen around the world and the phenomenon seems to be on the rise, according to Andrew Farnsworth, a scientist at the Cornell Lab of Ornithology who studies bird migration.