I'm familiar with the very soft vibration they emit. From what I have noticed with my lovebirds, they do so on the more quiet moments when they are lovingly interacting with their mates and are all puffy and glued together for either a cuddle or when one of them asks some regurgitated food.
I see this happy vibration as a positive thing, but I don't see mine vibrating all the time.
I have also noticed the same response with my Khaleesi, when I go close to his cage and start to talk sweetly to him. He does a very cute low pitched warbling sound and I can see a very slight vibration on his wings and body. Once I pick him up, take him out of the cage and give him a few kisses on his crop and neck, the vibration stops.
I see this happy vibration as a positive thing, but I don't see mine vibrating all the time.
I have also noticed the same response with my Khaleesi, when I go close to his cage and start to talk sweetly to him. He does a very cute low pitched warbling sound and I can see a very slight vibration on his wings and body. Once I pick him up, take him out of the cage and give him a few kisses on his crop and neck, the vibration stops.