My sister has a window attached hummingbird feeder that holds 1 cup of nectar and she fills it daily. She also has around 4 birds visiting the feeder - sometimes in pairs, sometimes individually.

My 2 cup hanging feeders need to be refiled at least weekly, sometimes more often but I seldom have crowds.....usually just solo birds.

And they don't suck, they lap. But they have a specially crafted tongue that makes it a much more efficient process than say a dog lapping a bowl of water. And they do it - like everything else - at a very fast speed. 18 times a second!!

OK, well, I've learned a few remarkable things. First of all, it is said that a hummingbird can drink, every day, anywhere from 1/2 to 8 times it's body weight. Zowie! Also, the tongue is like straw. It doesn't slurp through it, but when the straw-like tongue contacts the liquid, many drops of water are captured by it. The tongue can shoot out many times every second, each time bringing many drops of liquid to the bird.

So what I'm realizing is that these guys can and do chug pretty efficiently.

A hummingbird weighs about 4 grams. There are 240 grams in a cup. So if one bird really drank eight times it's body weight in a day, one bird would go through a whole cup in a week. So if one had a couple of birds that frequent the feeder, it would make it pretty easy to consume it all without having enormously thirsty birds. I'm no longer surprised that it disappears so quickly.