what fabric for protective cover for outdoor furniture?

[gotacola.livejournal.com]

I have an outdoor table but I always have to wash it down before I can use it as the birds make a mess of it between uses. So, I'm going to make a cover for it so that I just have to pull the cover off when I want to use it. I'm not sure what fabric to use. I want it to be as cheap as possible, probably washable (machine or spray down with hose), able to sew with my sewing machine, seal out water and to not disintegrate from the sun straight away. I'm thinking light canvas or plastic tarpaulin but not sure how either would go with my sewing machine. I'm hoping someone here has made one and can give me a hint. Thanks. :)