"Butterfly looking guy"
"Has the most gorgeous melancholy whistle. The one on the Wikipedia article doesn't come close."
The Sunbittern is the only bird in its family, Eurypygidae. Their closest relative is the Kagu (Rhynochetos jubatus) of New Caledonia, even though Sunbittern are found in South America. Their base plumage is good for keeping camouflaged, but they've got two large "eye spots" that they flash if startled or threatened. These can also be shown to other sunbitterns in courtship and threat displays.
Sunbitterns are reported to use bait or lures to attract prey into striking distance. They're only one of twelve species to do so, though this behavior has only been seen in captive birds.
Here's a clip of their song. It's that low, two-toned whistle.