The Yian Kut-Ku is a fire-breathing Bird Wyvern. They are rather small compared to other wyverns and resemble giant chickens in both manner and form. The name "Kut-Ku" may come from the word "cuckoo" for its bird-like characteristic and appearance. They inhabit the Forest and Hills, Jungle, and Swamps.
Yian Kut-Ku are the weakest of the boss wyverns, and one of the most basic wyverns but they are rather fast. Many hunters defeat the Kut-Ku as their first wyvern. While experienced hunters usually have no challenge in defeating it, first-timers may have some difficulty due to the Kut-Ku's speed.
They are belligerent towards hunters, and use their Fire attacks and pecks to defend their territory. If attacked before fully landing, it may opt to circle the area and swoop down on its foes. Though their attacks and speed make them more formidable than other small-sized monsters, they leave themselves open to attack more often than the average wyvern.
Due to their highly developed ears, Yian Kut-Ku have exceptional hearing. Their ears are effective for hearing prey and enemies outside their range of sight, but because of their oversensitivity, they are also vulnerable to explosive sounds. Dizzied upon hearing an explosive sound, Yian Kut-Ku are stunned and become open to attack, but may become enraged once the dizziness subsides. Its ears will break when they sustain enough damage, but once its ears are broken, the Yian Kut-Ku is no longer as susceptible to explosive sounds.
The Yian Kut-Ku's ears fold back when it is near death. This normally means that it will try to run away to recover its health.
In Monster Hunter Freedom Unite, there is a quest called "At Birds Hill..." which requires players to fight an extremely small Yian Kut-Ku at the Forest and Hills zone, which is most-likely a young Yian Kut-Ku. It has a different voice due to its miniscule size, yet its fireball attack increases in power and explosion radius.
This may be because it doesn't have very good control over its Flame Sac.
In Monster Hunter Frontier Season 8.0, 'Hard Core' Yian Kut-Ku became available. This variant can perform a circular rampaging charge attack with extreme attack power, and has the ability to spew a Fire Ball that causes a wall of fire.
In Monster Hunter Freedom Unite, Yian Kut-Ku can be sometimes be seen drinking from the ponds in Areas 9 and 10 of the Forest and Hills.
On Monster Hunter Frontier Online Yian kut-ku can be a pet, its favorite foods are insects and worms.