text:  Daybreak in Washington as the National Zoo's three biggest stars began their long journey home. A sad moment for three bears that are leaving with a little piece of our hearts from D.C. People are so sad that these pandas are gone. After five decades, time has run out on the Smithsonian's panda exchange program with China. It's the end of a conservation effort. And now, all these years later, we are bidding our giant pandas farewell.