I have a large outside aviary with four canaries in it, one male and three females, one of my canaries has stared to lay eggs and sit on them, and my question is when the chicks hatch is there any special food I should feed the mother etc?
Congratulations! You can give them soaked seed (it's more easily digested - just soak the seed for 4-6 hours, drain and replace with new stuff every day), egg food/song restorer, millet sprays and their normal food, plus greens they like. That's what my bourkes and finches have been given and they've raised quite a few babies this year.
Just keep an eye out for mice. I've recently had to raise some Java finch chicks (from a day old) after a mouse attack. One is missing most of his toes (it was a miracle he survived as he was so pale when I brought them inside from blood loss) and the rest are all missing at least one. The mice were eating my finch eggs too so now we have plastic down two sides and insect screening on the door end as the mice were squeezing through 1/4 inch mesh! What a nightmare!