What are birds hiding under their feathers?

THESE BIRDS DO THINGS THAT WOULD MAKE EVEN A PSYCHOPATH FREEZE

KOOKABURRA VOCAL CORDS

Bird Songs - 8 HOURS of Birds Singing in the Forest - Nature Relaxation Video in 4K Ultra HD

Relaxing Bird Sounds 4K ~ Birds Singing Heal Stress, Anxiety And Depression, Heal The Mind

Relaxing Bird Sounds 4K~ Birds Singing Heal Stress, Anxiety And Depression, Heal The Mind