Reston has a custom of bird counting, and the results are just in. The birds which are most common here, in mid-January, are birds which don't belong here: specifically Canadian geese and American robins. They both should be south of here, or at least that's my understanding.
A little Googling reveals I'm mistaken, as is much too often the case. Robins (the males stick around to fight for territory in the spring, the females being wiser head south).