On a less alarming note, whoever came here wondering about what it means when a cockatiel dips its head, you've come to the right place! When a cockatiel dips his head and spreads his wings like Audrey is doing below, he's flirting with you.
This position is referred to as a heart-shaped pose (Update: or more commonly known as heart wings, as Cyndi mentioned in the comments). The best way to respond is to play along with him by dipping your head, making kissy noises, etc.
The dipping behavior is also a way to determine if your cockatiel is male or female. The males flirt and sing. The females enjoy being flirted with and sung to.