It is amazing how well they will fit. I wouldn't mess with the nest now since she is laying and sitting, if you do, she might abandon the nest.
A Gouldian is an Australian finch, one of the babies I bred is in my avatar. They are on the endangeres species list and are notoriously hard to breed. Recent studies even show that the hens in this breed choose the sex of their offspring!!
Here are some photos of my birds:
Adult hen

Fledglings (a day or so before really flying)

Adult males


Chicks just a few days old, your canary chicks won't look much different

Chick about 5 days old. Note the crop looks huge and surrounds the neck, this is normal.

And here is a photo of my prize girl, she ended up having a blue breast because her father is a melanistic bird (his colors are darker and a bit richer than normal)
