If you had a bird in your hand, how many would have to be in the bush to let it go?

If there was only two in the bush and you let the one in your hand go. You probably wont catch the two because they are fast, leaving you with nothing. So how many would there have to be in the bush for you to risk catching more or going home with nothing? Could be any type of bird, chicken, parakeet, owl, eagle, finch or what ever. Could be for a pet or hungry or you just wanted to kiss one. What if you had a net? Or a rifle?