You can see how bird feathers work for yourself. First, go to a park or a place where there are pigeons and find a bird feather. Or you can buy nice clean chicken or duck feathers at a craft store.
Hold the feather in your hand. You'll feel that it is very light. Feathers have to be light so the bird won't be too heavy to fly. Now cut through the tube in the center of the feather (the rachis) with a pair of scissors. See how it is hollow? That is what makes bird feathers so light and strong. A hollow tube is a very strong shape; your bones are made the same way.
Attached to the central tube are thousands of long hair-like things called "barbs". They stick together to block the air so the feather can push against the air, like you have to keep your fingers together when you are swimming. The barbs stick together because they all have many tiny hooks, called barbules or "little barbs". Each barb hooks onto the next one, like Velcro. You can see the barbules with a magnifying glass, or even better with a microscope.
Barbules on a feather,
thanks to Blister Microscope
Another great project is to observe how birds behave. Sit down outside, in your yard, or on your front stoop, or in a park, and wait for some birds to fly by. What are they doing? Where are they going? Can you catch them eating something? What is it? Where is their nest? What kind of sounds do they make? If you are thinking about a science project, you'll want to first formulate a hypothesis, then observe the birds to find out whether your hypothesis is true. Maybe you could take pictures of the birds to show how they behaved.