Let's talk about hummingbirds! Hummingbirds flap their wings super fast. This helps them stay in one place, or hover, in the air. They do this when they want to reach the sweet nectar inside flowers. Hovering lets them drink the yummy nectar without falling or flying away.
Also, your sentence should say: "Hummingbirds flap their wings super fast, which lets them hover so they can reach sweet flower nectar." This makes the sentence clear and easy to understand!