Need help identifying baby birds

by Courtney
(Grassflat, Pennsylvania)

These 3 babies were brought to me as new hatchlings that neighborhood kids found and were toting around.. no mother bird or nest to be found.. i have had them for a week now and they seem to be doing well but i do not know what species they are ( i was thinking they were robins ) and would like to be able to give them the most specialized care i can... any help would be greatly appreciated... I live in central Pennsylvania...