Scientists have found that birds are an important way that ticks are carried to new areas and that sometimes those ticks are carrying disease-causing organisms. In one study, 9 species of ticks were collected from 33 species of passerine birds (these are songbirds or perching birds). Some birds migrate from as far away as South America, then redistribute the ticks as they fly throughout North America.
In another study, researchers found that about 7% of the birds examined were carrying ticks. Over half of these ticks were infected with microorganisms that cause disease in humans, including Lyme disease, human granulocytic anaplasmosis (HGA), and human monocytic ehrlichiosis (HME).