The Northern Cardinal is perhaps responsible for getting more people to open a field guide than any other bird. The male is a perfect combination of familiarity and style in a shade of red that can t be missed, especially in snowy backyards. Even the female bird sports a sharp crest and warm red accents. The female cardinal is one of the few female North American songbirds that sing, and she often sings while sitting on her nest. From spring into summer, their sweet whistles are one of the first sounds of the morning.The Cornell Lab of Ornithology has developed Qr codes which allow you to listen to the songs and calls of hundreds of birds, right from your smart phone. We have harnessed this educational technology to allow you to hear these birds sing while completing your puzzle. The Qr code is on the back of the box.