Our big run has no natural cover, and we lost a hen to a RTH late last summer. So we provided some unnatural cover for them! We screwed a sheet of corrugated roofing metal onto two sawhorses to provide a little roof about 8' x 3' to shelter and shade for the chickens. (This has now become their favorite spot to dust bathe and just hang out, it's like their coffee clatch!). We also put two pallets together into an A-frame formation for quick cover if they need it, and dragged an old table out into the middle of the yard as another shelter. This all makes the yard look a bit junky, but we haven't suffered any additional losses, though i know the hawk is still in the area. When they come out of the yard to free-range they have lots of options for cover.