So I just sat outside for a little while and I suppose this is the thieving hour because I just watched a couple of these little friends: http://ucsantacruz.ucnrs.org/wp-admin/images/researchpics/ylrbirds/House_Sparrow.jpg some house sparrows, ripping pieces off of my lettuce plants and flying away. They barely paid any mind to me coming toward them until I was about 3 feet away. My dog just watched lazily as the birds tore apart my greens. what do they want it for? are they eating it? building a nest? can I offer something else that will make them lose interest in my salad greens?

Bird netting. I wouldn't feed them or you'll have them forever, you'll find them more interested in seeds, seedlings, fruits, berries than in insects - so not particularly beneficial to have nearby.

They seem to like my spinach and lettuce more than anything else

I've done as much as I can to discourage them here, including removing their nests when they take over bird boxes - or we'd have no native birds in the neighborhood at all. We agreed as a neighborhood to not put out food other than nyger seed for finches and chickadees (the clinging type eaters) etc (sparrows can't eat from those feeders) and hummingbird feeders, that's helped enormously.
There were so many sparrows for a couple of years we were honestly considering trapping the males but it didn't come to that - and now we have mosquito eating swallows back and nesting every year :)

The plastic bird netting is inexpensive and easy to handle, you can roll it back up and use again next year if you have to.

Here is a link that might be useful: Sparrows

Just let them live. Give them bird feed and they wont bother you