Did this birds mom find him?

so we recently found a northern mockingbird in the street near my school, from what i learned it is a fledging and my dad didnt know to leave it but anyways weve been taking care of it and its learning to fly and doing great but recently ive been seeing a older mockingbird screeching sort of and singing and looking at the window where i let the fledging get some air and look outside where it will be soon after it gets a little better at flying, but anyways i usually see the bird outside looking at the fledging, is it the mom? because my school is literally behind my backyard and i found the bird down the street so since i live so close to where i found the fledging is it the mom thats outside? or is it a competator bird that wants to attack the fledging, if so then ill keep the bird for a little longer and keep feeding it mealworms since they have protein and it will get strong and it can beat up the bird outside? ohh and if your wondering it has a whole entire room to fly around in its not that big since were not rich but its a good sized room and it cal fly around all over it