It's said that rodents can fit through a hole the size of a nickel. Obviously, they'll be able to fit through unprotected ventilation holes in your eaves.
Many homeowners are not even aware that such holes exist in their eaves. These holes are essential, so you can't just slap wood over the top of them. In fact, even wood would hardly repel rats, mice, and birds--many of which can easily chew through wood.
Buy Direct - Ace Hardware Cloth, 1/8" x 1/8" weave
Buy Direct - Ace Hardware Cloth, 1/4" x 1/4" weave