Colleen Cahill - 2015 Smithsonian Photo Contest

Regions near the Mexican border are home to this gnome, the tiniest owl in the world, no bigger than a sparrow. On moonlit nights in late spring, its yapping and chuckling calls (surprisingly loud for the size of the bird) echo among the groves of giant cactus and through the lower canyons. The Elf Owl feeds almost entirely on insects and other invertebrates, which become harder to find in cold weather, so it migrates south into Mexico for the winter.