Why do most birds not prey on hypolimnas?

Most birds do not prey on Hypolimnas butterflies because they are unpalatable due to their toxic compounds acquired from their larval host plants. These compounds make them distasteful and potentially harmful to predators, leading to a learned avoidance behavior. This phenomenon, known as aposematism, serves as a form of defense mechanism for the Hypolimnas butterflies against predation by birds.