This results in an inability of the bird to sustain flight which is observed in the early stages of botulism. Once this has occurred, birds suffering from botulism are commonly observed propelling themselves across the water with just their wings. The next effect to occur is paralysis of the inner eyelid membrane followed by paralysis of the neck muscles. Loss of flight and limp neck are the most recognizable signs of avian botulism. Once birds reach this stage, death from drowning often occurs before they reach the next stage or respiratory failure.
Losses vary from year to year and from species to species.
A few hundred birds may die one year at a specific location and tens of thousands the next year. The unfortunate problem associated with avian botulism is that bacteria formed in these carcasses are quite stable and can serve as the source of outbreaks for many months to come. In dealing with avian botulism, the emphasis should be on prevention and control of outbreaks, rather than treatment of sick birds. Identifying possible cases of avian botulism at the early stages is the key to effective control. Public awareness of the conditions that lead to avian botulism and prompt corrective action can greatly reduce the epidemics which now claim hundreds of thousands of birds each year.