This protozoan infects birds, causing lesions in the upper digestive tract that may lead to death. It is a common parasite of pigeons (Columbiformes) and has been implicated in the extinction of the passenger pigeon (Ectopistes migratorius). In 2005 it spread to songbirds in Britain and citizen science studies showed that it caused significant declines in greenfinch and chaffinch populations there. (Robinson et al. 2010). Scientists suggest it also afflicted Tyrannosaurus rex (Wolff et al. 2009).