Their legs are longer than their necks. When the grass is shorter than 4 inches or so they kneel like that to get at it. I happen to think its a recent adaptation to utilizing groomed lawns as a food source.
Flipper, from what I can tell from that picture it looks like early post break-up(what we call spring). The snow's gone from the open areas but probably still deep out in the woods where the ground is still fairly well shaded. The moose will come out and try to get at the still green hold-over grass close to the ground that was protected by the snow. The brown grass you can see in the pic looks like the normal winter killed upper half of the grass blades.
I don't belive there are any grasses out yet that will stay green under the extreme cold and snow that the northern climes bring..Even here...It doesn't take long, after the snow is completly gone and the day's actually start to hit in the upper forty's and fifties to start to green up though....