This tray of whooper eggs has just come out of the incubator. The eggs will be examined, candled, and weighed to see how their development is progressing. Eggs lose weight during incubation as the chicks grow and use up yolk and fluid. But if an egg loses too much weight too quickly, it can be helped by special treatments or placed in a separate incubator that has a higher humidity level. (Photo by Nelson Beyer, USGS Patuxent Wildlife Research Center)