In the spring and summer birds look for new homes to build their nests, lay their eggs and raise their young. Unfortunately sometimes their new home is inside your chimney. It’s a perfect place for them, the chimney is high up and provides protect from the weather. There are simple ways to keep the birds from living in your chimney. Birds are not only pests when they nest in your chimney, they can get inside your house. Birds can bring mites, fleas, and other parasites.
Use a chimney screen. A chimney screen is a piece of wire mesh that fits across the opening at the top of your chimney. It usually attaches with 4 screws. It's a pretty easy do it yourself job. Chimney screens come premade and can be found at local home improvement or hardware stores. Check your screen every year and after storms for damage.
Have a chimney cap installed. This is a cap that has holes to allow smoke to escape through mesh sides. Depending on the size of your chimney and if it has a double flue, may need to be professionally installed. A chimney cap has an advantage over the screen because it also keeps out water and small debris.
You can also buy an ultrasonic device which emits a high pitched sound. Humans cannot hear it, but it scares birds away. This offers no protection from water and debris. An ultrasonic device is usually used in conjunction with a screen or chimney cap for persistent birds. These can be found at local hardware stores and home improvement stores. They are also available online.