Another funny looking bird with a funny name, like its cousin the whip-poor-will. Night jars are strange looking creatures and wonderfully camouflaged...when they're on the ground or against a tree trunk. This one didn't seem to grasp the concept of camouflage, sitting up on a green leafy branch against the sky where he stood out a bit
The eyes are usually more slit like this during the day - they either nap with eyes closed, or open just a slit to make sure all is safe...but the eyes can open up fully and much larger...I think they'd likely only do this at night though, as they're nocturnal birds with great night vision much like owls. I've never seen the eye open any more than a small almond shaped slit.