You're talking about the bands of the parents? If so......you can do that anytime in the next month. They'll sit on the eggs and then feed the babies for 30 days. Since you haven't got the band numbers yet, I'd just wait until the babies hatch and are around 10 days old. Don't want to break the eggs trying to remove a parent just to write down the band number.This is great. I already have two eggs that are in nests. How long should I let them sit on the eggs before I attempt to take down the band numbers? I dont want them to abandon them.