The rectangular shelters located in the occasional alfalfa field around Powell house leaf cutter bees. Smaller than honey bees, leafcutter bees are used to pollinate seed alfalfa crops. Leafcutter bees are not social; they don't gather in hives, although female leafcutter bees will nest close to one another. The shelters house boards which have been grooved and fitted together to form small "tunnels" where the bees lay their eggs. The bees then pack the eggs in with leaf fragments they have chewed off. The boards are protected during the winter, and the next season the eggs hatch out and the cycle starts again.