Place it in a paper towel lined small box with air holes, and call your local wildlife center. They will be able to direct you further. Do not handle the bird other than the initial lifting and placement.
Additional response from Liz @ the Sarvey Wildlife Center in Arlington, Wa.:
After you have covered the bird, picked it up and placed it in a small box with air holes lined with paper towels, place it in a warm and quiet room. As soon as you are able to, bring the bird to us at Sarvey Wildlife (or your local wildlife center). If it is a long trip to do so, try giving the bird some Pedialyte with a little water to sustain them. Continue reading