My hummingbird feeder has been completely drained (of at least two cups of sugar water) at night for the past week. [I have plenty of hummingbird visitors (although fewer than last year), but I knew they wouldn't be feeding through the night.] I had a short list of possible suspects and last night I did a stake out. Alas, I don't have the necessary camera equipment to i.d. individuals, but I'm sure it looked something like this!
Still shots here; Movie here. Both links from Beth at fireflyforest.net