How many remember the song from the movie, Mary Poppins, Feed the Birds? That song always comes to mind when I go out to fill the bird feeders.
I feed my birds year round, even though they don't consume much during the middle of summer. It is a good idea to keep the feeders up all year because the little birds do become dependent on the food. Especially if growing conditions aren't quite right for an abundance of natural food.
I have several feeders scattered over my front and backyard. I also have two placed in front of my dining room windows which our Kitties LOVE! We call it our Kitty TV. A great way to keep them entertained during cold weather. Especially when the squirrels come to visit.
In addition to food. It is important to provide fresh water for the birds in the winter months. In temperate climates, it is fairly easy to keep the birdbaths filled. But in colder climates a person must either carry water out every day or invest in a birdbath heater. I have found that I had a lot more birds come visit my feeders once I put out water for them.