Baby bird help?!?!? URGENT!!?

Ok so theres a baby bird in my backyard. It doesnt know how to fly. Its been sitting in my backyard on a branch just chirping for about 5 hours. Literally. Theres no bird chirping that sounds like it so i dont know if its parents are around. I just want to know if its going to be okay at night? Why are its parents not there? Do I need to help it? Are its parents going to come for it?