I was wandering through the forest in western Washington when I heard a series of high-pitched, whistling bird calls. As I peered into the foliage, I finally made out the Cedar Waxwings that were making the sound. Another time, I was in southern Texas, along the Rio Grande border. Again, I heard birds singling some very high notes. In this case, they were followed by a series of lower notes and a distinctive two-tone call. I realized that I was surrounded by a number of Ruby-crowned Kinglets.