Growing Chicks

One of our hens hatched two eggs. The chickens are growing fast. One of them kept escaping when I opened the door of their shelter to replenish their food and water. (I have them in a shelter inside the coop to protect them until they are big enough to join the other chickens.) The chick would chirp in alarm when I grabbed it to put it back inside. The second time the chick escaped, the Mama got very upset, fluffing her feathers and clucking angrily. I was afraid she was mad at me for "threatening" her check when I put it back inside. But since then the chicks have backed away whenever I open the door so I realized she was scolding them, not me.