Since the 1960s he has used radar to measure migration across the Gulf of Mexico. Check out the June 1993 National Geographic magazine for Dr. Gauthreaux's article and photos. If one oriole weighs 40 grams, that's .09 pounds. A ton is 2000 pounds, so divide 2000 by .09 for an answer of 22,222. Plus there are not a lot of people up at night and it's safer.
Songbirds eat during the day plus sleep in the day and travel during the night.
Many songbirds, including orioles, fly at night and land to rest and feed during the day. The students are right about night being safer, too. Hawks and other songbird predators can't fly at night. There are many other reasons, too. At night, the winds die down so flying is smoother.