Pearson 1982 Rhea April 8-10. Cavallon Bonto, Rio Negro. In three days here, gone in and out twice each day = 6 trips of about 2 hrs along the grassy rolling, have seen rheas every trip. The most in one group was 13. They are usually grazing on the periphery of a flock of sheep, never with the cattle. When frightened they run up into the bushy stuff, sometimes giving the same wing-flash and zig-zog as the Peruvian rheas. Their big droppings are everywhere, containing coarse vegetable fiber and maize seeds.