Ostrich chicks hatching. When ostrich chicks are hatching, the recommended relative humidity of the hatcher is 25%, although this may vary depending on individual characteristics and egg size. Higher humidity may lead to wet, edematous chicks. Before a chick is removed from the incubator, the area of the yolk sac on the ventral body wall should be examined to ensure that there has been proper involution; if so, a 7% iodine solution may be applied to the area to protect against infection.