As recently as 200 years ago, flocks of passenger pigeons numbering in the billions blanketed the North American sky. By 1914, the species had been wiped out by merciless hunting campaigns. Now thanks to cloning technology, the animal that was once the most numerous bird in North America might have a second chance. Museum specimens, feathers and other remnants of these birds still exist, and because they are so closely related to the mourning dove, finding a surrogate mother would be easy.