What characteristic distinguishes a passage bird from an eyass?

A passage bird is distinguished from an eyass primarily by its age and developmental stage. Passage birds are generally older, having fledged and migrated, while eyasses are young birds that are still in their nest or have just recently left it. This age difference is critical in understanding their behavior, training needs, and suitability for falconry.

While migration status is indeed relevant—the passage bird refers to those that are migrating or have completed their migration—what truly sets them apart from eyasses is most explicitly the stage of life they are in, which relates back to their predetermined age classifications. Understanding these distinctions is essential for proper falconry practices, particularly in terms of training and rehabilitation.