When you have your camera on a tripod remember to turn off the image stabilization on your lens. This will give you a sharper picture. Photographers use tripods to reduce camera movement when taking pictures. A cable release will also further insure that there is no camera movement.
I have had good luck photographing birds on my back porch using a tripod and a cable release. I purchased the Canon Remote Switch RS60 E3 and the Steren 2.5mm Stereo Audio Extension Cable – Sub-mini phone Male Stereo – Sub-mini phone Female Stereo – 12ft. You can purchase two of the cables and you can photograph right from inside your home while the birds are enjoying the food you have put out for them. Below are some sample pictures I have managed to get using this technique.