RIO GRANDE CITY, TX - DECEMBER 07: Migratory birds fly south over the U.S.-Mexico border on December 7, 2015 near Rio Grande City, Texas. Border Patrol agents continue to detain hundreds of thousands of undocumented immigrants trying to avoid capture after crossing into the United States, even as migrant families and unaccompanied minors from Central America cross and turn themselves in to the Border Patrol to seek assylum. (Photo by John Moore/Getty Images)
