I came on an adult bald eagle with a broken wing one morning. I called our Game Wardens, and one responded and had clearly done this before. He had me hold a blanket on one side of the bird while he put on a pair of heavy leather gloves and pounced from the other. My job was to distract until he grabbed the legs, then drop the blanket over the head and wings.
He grabbed it in one try, stuffed it into a big dog cage, and I delivered it to Avian Haven, a local animal rescue spot. It had a broken wing and we could already smell the infection, and the bird did not survive the first night after "rescue".