In terms of intraspecies communication, owls use a variety of vocalizations to communicate with each other. These vocalizations can be used to establish territory, attract mates, and communicate with their young. Owls also use body language to communicate, such as raising their feathers or spreading their wings.
The best-suited modality of intraspecies communication signal for a nocturnal species owl would be vocalizations. Vocalizations can be heard over long distances and can be used to communicate even in low-light conditions. Owls have a variety of vocalizations that they can use to communicate with each other, which allows them to communicate effectively even in the dark.