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After hatching it can take over a month before the chicks are ready to leave the nest. They will be able to fly.
Before they leave you'll notice them teetering on the edge and flapping their wiings, stretching out and looking like they're ready to take off.
Nature provides a wonderful instinct and birds are remarkable at learning. Even if they fall from the nest, many babies will survive long enough for you to gently (preferably with a clean towel or glove on your hand, put them back in the nest. It's not because a parent will smell the human on it and reject it (old wives tale), but because the natural oils and chemicals from our hands may be harmful to very young ones like this that don't have full feathers in.
Be prepared: Some birds will toss chicks out for unknown reasons. Sometimes it's because the parents are young and inexperienced, other times it might be because the chicks are failing to thrive (something's wrong with them) and it could also be due to stress and too much attention by humans in the aviary area.
If a chick gets tossed, again, pick it up and replace it as often as need be - until you're pretty sure it's not going to be accepted back. Then you'll need to make the decision to hand feed it (whenever you're breeding you must be prepared to do this) or have it humanely euthanized at any local vet.
Here is more info about breeding canaries