HAMER — The sound of hundreds of greater sandhill cranes gleaning a harvested field of corn means that fall has officially arrived. I arrived before daylight last Monday morning as I could hear flock after flock fly in from the north to drop into a field just south of Camas National Refuge Area. When it got light enough for me to see, there were close to a thousand of the large birds in a plowed corn field filling their bellies with the tasty morsels. As it got lighter, I watched as the cranes came in very high, before circling and dropping into the field. It appeared that they had been flying…