My rooster wobbles his head, does anyone know why?

Hello I was given this flock of sweet chooks, 5x hens and this rooster, the rooster wobbles his head and I was told he has done this his whole life (2 years old)

Does anyone know what the cause is? Its his only behavioral quirk, besides that he is a kind rooster 🐓💗

The background noise is a child babbling, not the chickens 😇