At dawn Sunday the younger and smaller of the two whooping crane chicks was missing. Ten zoo employees slashed the undergrowth with scythes and crawled through the grass in a vain search. George Douglass, zoo director, feared that an owl or a rat had made off with the weaker chick during the night. Immediately he had a small-mesh wire fence built, reducing the pen to one-sixth of its former size. Workmen also were covering the pen with a wire roof to keep out further marauders. At last report chick No. 1 was in fine shape—husky, always hungry and growing fast.