What do I do with a Baby bird ?

for the last couple of days, I have been trying to nurse back a baby pigeon that fell on my balcony. Now it just crouches in a corner and hardly does anything. But, I do see a pair of older pigeon's always around, I am thinking its the parents of the poor bugger.

I am getting a little zissed off and want to throw this little bugger over the balcony (no not literally !) but, rather take him down and throw s/he into the bushes. As you can see, my cat seems to love to stalk it !!