Student or Learner
This "these gentlemen who did the early collecting and classifying" seems kind of rare as it refers to "their". Is this common?
ex)Scientists regarded sight records as unreliable and held fast to the principle that specimens were the ultimate standard in the study of birds....But on the other hand, because they were often unable to work with fresh specimens, the scientists had to rely more than ever on the skins amassed by the old amateurs. But who were they? What were their standards, these gentlemen who did the early collecting and classifying?
(Not a Teacher)
I've seen and heard that form used plenty of times before. I'd say it's certainly accepted in academia and literature.