Cockatiel with unusal bubble like lumps

Sparky; our 16 yr old cockatiel has unusual bubble like lumps at the back of her neck, they do not appear to be filled with anything other than air and literally look like bubbles made from a thin layer of skin. I can see veins in the skin of these bubbles. She does not appear to be in any pain she is eating drinking and exercising as normal.

Until I looked at this page I thought that 16 was quite an old age for a cockatiel but fom reading other comments I can see that she is actually still quite young. Sparky has had these for at least a couple of weeks. Do you have any idea what these could be?