The lowest-maintenance my yard has ever been--and there was a full garden, too-- was when we had 1 duck and 2 geese. Geese are herbivores and won't eat the slugs, but the one duck took care of all of them. The geese kept my yard very well-groomed, thick and healthy, not to mention weed-free, since anything that remotely resembled a dandelion was a real delicacy and got eaten first. I ended up selling our lawnmower, because the geese did a better job without me. Completely effortless yard and garden, and the grass was always the right height and super thick. There was a little poo buildup in summer and dry season, but that was easy to remedy with a hose. It just fertilized the lawn.
The only problem I had was when we ran low on slugs--even with just one duck it does happen eventually--and the fowl started conspiring. I don't know how this started, or who's idea it was, but the goose would walk up to my "round on the ground" vermicompost bin with the duck, bump the bottom of it so that some of the red wigglers came out, and stand there waiting as the duck snatched them up!
