Brown cowbirds lay their eggs in the nests of red cardinals. The cardinal parents raise the unrelated cowbird chicks and provide them with food that would otherwise have been given to their biological offspring. A researcher conducted an investigation to discover the types of symbiotic releationship between the cowbirds and the cardinals, and discovered that the nests containing only cardinal chicks were more successful than the nests containing both cowbird and cardinal chicks. IDENTIFY and DESCRIBE the most likely ecological relationship between the two species.