Bird Wyverns (Japanese: 鳥竜種 Chōryūshu) are a class of monsters introduced in the first generation. They are a small to medium sized class that includes Flying Wyverns with slender bodies that are bipedal and, in some cases, either have wings or lack wings. There are two distinct types of Bird Wyverns: Flying Bird Wyverns and Theropod Bird Wyverns. Flying Bird Wyverns exhibit similar characteristics to True Wyverns, with a bipedal stance along with developed and functional wings. Many of these possess a hard, sharp beak which can be used to peck at attackers, and generally behave in a bird-like manner. Theropod Bird Wyverns are reminiscent of Brute Wyverns: flightless, bipedal creatures with long tails and powerful legs. Unlike Brute Wyverns however, these monsters are generally quite small. Furthermore, Theropod Bird Wyverns almost always live under a social hierarchy, with young individuals, females and beta males led by a strong, dominant alpha male, which can command and control his subjects during combat.