Canary bald spot

by Meriem
(Ireland)

Hi,
I'm minding 2 canaries for a friend (1 male-yellow, 1 female-green).
They seem to be comfortable in my home now but recently I noticed that the Female bird has started to fluff up her feathers very frequently (she ends up looking like a ball of feathers!!) and she scratched at a spot behind her head which now appears bald.
Other than this, the birds are fine, they eat drink and move around their cage as normal....

They did however abandon their nest when they were placed in my care (2 weeks ago)...I called the vet and he said that it was due to the stress of the new location...Could this have anything to do with it??

Please help as I don't want anything to happen to them while in my care!!