Made from durable 100% cotton duck, Carhartt's Bib Overalls are the perfect choice if you're going to be out in a field. Whether you're actually doing work, shooting dove, or just standing around a fire drinking beer and bourbon, it's hard to think of a better alternative. While the workwear thing may be popular with hipsters right now, hard-working people have been wearing these for decades and fortunately, they will most likely never be sold in a boutique store in New York City. Find them at your local hardware store, or other place where manly things are sold. If you're south of the Mason-Dixon line, you'll want to get the unlined version, but I don't have to tell you that.
Oh, and while you're at it, pick up a pair for your girlfriend; you won't be sorry.