Enteritis as a cause of mortality in the western bluebird (Sialia mexicana)

Increased mortalities in adult western bluebirds utilizing nestboxes were n oted in western Oregon during 1998 and 1999. A necrohemorrhagic enteritis w as found in 8 of 10 birds submitted for necropsy. Acanthocephalan parasites were present in four of eight birds with enteritis. Microscopic changes co nsistent with necrotic or ulcerative enteritis were commonly present. Anaer obic Culture of the intestine yielded Clostridium perfringens in three of t hree birds. Genotype analysis of two of these isolates revealed them to be C. perfringens type A. Bacterial enteritis is believed to be the cause of t he increased mortality rate, but further investigation is required to prove a definitive link to a clostridial agent.