I agree with Eric; and I carry a little 4x monocular. By definition they are 1/2 the weight of binoculars, holding all other variables constant. Stereoscopic vision does not work out at that distance, so one eye is as good as two for most viewing, I think..
Coincidently it attaches to the lens of my Casio EX-Z750 camera, to increase the optical magnification from 3x to 12x; works ok in bright light.
Last month I was observing the wild monkeys in Niigata with the monocular; nice to have it.