How do you know if a mother bird has found her babies I was trying to put a baby swallow back in its nest and all the babies just flew out and now they are all missing?

If a mother bird has found her babies, she will typically return to the nest and call to them, encouraging them to come back to her. You might observe her flying nearby, chirping or bringing food. However, if the babies have fledged (learned to fly), it's natural for them to leave the nest and explore their surroundings. If they are not in immediate danger, it's best to leave them be, as the mother will likely continue to care for them from a distance.