Yes, you can use bird’s cages for rats but after assuring that the size is correct. Also, you have to make a few modifications here and there before letting your rat enter. For example, a bird’s cage usually includes a food container, perch, or handle. To make it apt for rats, you can put exercise wheel, make levels, dividers, or maybe sliders and other activities for him to play around with. Rats do not sit idle like birds, and therefore, need engagement. You can bring your creativity to make it the best possible crate for your pet rat.