Every fall Croton's jays migrate south. The jays always join flocks of migrating crookbeaks with which they share the same summer and winter territories. If a jay becomes separated from the crookbeaks it is accompanying, it wanders until it comes across another flock of crookbeaks. Clearly, therefore, Croton's jays lack the navigational ability to find their way south on their own.Which of the following, if true, most strengthens the argument?
【选项】Species other than Croton's jays occasionally accompany flocks of migrating crookbeaks