Did you know that opening a birdhouse to look inside will not frighten the mama and papa birds away? You can take a quick peek inside to count the eggs, check on the young, and make sure everything looks okay.
There is however a certain time frame when one must NEVER take a peek inside. From the time the baby birds are 12 days old up to 18 days old, please do not look inside a birdhouse. If you do, it may give the young birds the idea to leave the nest too early and the baby birds will not be able to fly away on their own.