A method for making a sex determination in avian hatchlings involves the following activities. A process line is equipped to process an endless plurality of hatchlings. The process line has an ultrasound inspection station for the hatchlings. The ultrasound inspection results are analyzed to find the presence of given sex-determinative structure for each hatchling. If the given sex-determinative structure is found then a first category assignment is made. The hatchling is sorted according to its category assignment. The category assignments might number two or three or so including positively-identified one sex, positively-identified other sex, and default to waste for any of various reasons.