Yep, this is nesting behavior for sure! Hopefully they will be fertile as well since you saw them mating beforehand. Sometimes the first few batches of eggs will be clear though, even if they have been mating, so don't give up if these don;t hatch. Good luck! :)
if it is the breeding season i am sure they are going to lay eggs soon but make sure u dont disturb them
YES you will have eggs anytime now. The signs are all good for eggs. Best of luck.
OK first of all, how long has the nest been there for, usually it will be 10 days before they start to lay, this is because they check out the nest box to see if it is safe. It probably is going to lay eggs, if it does, don't worry if it doesn't sit on them straight away, usually a hen will wait until she has laid at least 2-3 eggs. If there is no male the female will stil lay an egg but it wont hatch.