Recent studies have shown that there are certain blood parasites and strains in Spotted Owl, which make them have a much more fragile immune system that previously thought. This study was the first to show a Spotted Owl infected with avian malaria.

The initial study was conducted in order to investigate blood-borne parasites in birds of prey. Heather Ishak, a SF State graduate biology student, discovered that 44% of Northern and California Spotted Owl subspecies carries 17 strains of blood parasites. What is even more alarming is that they also carried a high number of strains which were not found in other owl species.

Researchers believe that the infected Northern Spotted Owl might have been exposed to these parasites by coming into contact with mosquitoes that had fed on a Barred Owl, which are now known to compete with Spotted Owl for food and nesting sites.