squirrel

Hello, Well i live in the city in an apartment building on a third floor and i notice that in my window there a squirrel that has made , what look like a nest out of tissues and napkin. Am a little worry about the squirrel because i don't think this is a safe place since its the the 3rd floor and its on the edge on the window, am afraid it may fall down or even worst am afraid it may be having babies and it going to give birth on the window and the babies might fall. When ever am home i check on the squirrel and it there either sleeping under the tissues or sometimes its moving or looking in my apartment. I was thinking of getting a shoe box and putting it on the window for the squirrel and attaching the box to the child safe window guards to secure it from falling, but am not sure if i should . Since the squirrel is alway there. And it has fallen yet so maybe i should leave him or her alone. Help? Please, thank you.