The Potoo Bird
Potoos are a group of near passerine birds related to the nightjars and frogmouths. They hunt from a perch like a shrike or flycatcher. During the day they perch upright on tree stumps, camouflaged to look like part of the stump.
The potoos are highly nocturnal and generally do not fly during the day. They spend the day perched on branches with the eyes half closed. With their cryptic plumage they resemble stumps, and should they detect potential danger they adopt a “freeze” position which even more closely resembles a broken branch. The transition between perching and the freeze position is gradual and hardly perceptible to the observer.
Potoos are monogamous.
Possibly because it's hard to find a mate with a face like that.