Everyone gave good advice, all i can say is if his cage is open, watch out for open windows. They are fast flyers, so clip his wings maybe, idk but i had a bad experience when i was little. I had 2 parakeets and my cousin came over one day and opened their cage and the window was open and my little Judith flew out
So just be aware, oh and also some of them learn to open their cage doors. I had a couple that did that, they just push it up with their beaks if it is the kind that just slides up. I used to put something on it to keep it closed.