Seventeen years ago, when she adopted a neglected, orphaned thirty-year-old parrot named Tiko, the internationally renowned ornithologist Joanna Burger entered one of the most complex relationships of her life. Sullen and hostile when he entered Dr. Burger's home, Tiko gradually warmed up, courting her during mating season, nursing her vigilantly through a bout with Lyme disease, and for a while even fighting her husband for her attentions. In time...