Birds that died from tick paralysis, each with an attached female bird tick. Mourning dove Paralysis begins in the feet and legs, progressing upward to affect the wings and thoracic muscles. Death is usually attributed to respiratory failure following paralysis of the diaphragm muscles. Hemorrhaging of the lungs and gastrointestinal tract are contributing factors. If the ticks are removed before the paralysis progresses too far, birds generally recover, often with dramatic results, within a few hours.
Affected birds become lethargic, often exhibiting lameness and a staggering gait.
As the paralysis progresses, they are unable to perch, have difficulty flying, and are seen crouching or lying on the ground. Although most cases involve only a single tick, up to 36 ticks per host have been observed. Cases often are reported around bird feeders where abnormal behavior of parasitized birds is likely to be noticed. Seasonal occurrence of tick paralysis of birds in Alabama, based on 85 cases, 1986-1999. Other species of birds in Alabama that have been found to be parasitized by I. brunneus without exhibiting signs of paralysis include the blue grosbeak, indigo bunting, and rufous-sided towhee.