Is this breeding behavior?

[Azalea]

There are a few spots of bare wall/chipped paint on the bird room walls.

A few days ago, Willow (female Budgie) suddenly became interested in a bare spot above the Budgie cage, where it's easy for her to stand and peck. Of course, Basil and Topaz joined in (Basil often follows Willow, then Topaz follows Basil). Now, both of the Cockatiels want to join in. They've chipped a decent amount of paint away, making a bigger bare spot.

My husband wonders if Willow is trying to create a hole for a nest? Is it possible? Her cere is still white, not turning brown.

[Loz]

It's possible that it's related to the breeding instinct but my experience makes me think that it isn't an indication of an imminent breeding event. I think it's the female chewing something on general principle and the males are joining in in order to appear helpful.
Tiels seem to require no reason at all and no invitation for a a good chew.