I've hand raised a dozen or so yellow nape babies. Some from near hatching and I've never seen anything resembling a preen gland on them. Not even a bump at the base of the tail. Here's a couple pictures of one of my 2010 babies at about the age you would be able to see something at the tail base. Nothing there. If anyone who's raised other amazon babies has a pic of this gland, I'd like to see it. I've never seen a bump or anything resembling it on my Hy girl either. Its just smooth skin and feathers. Now in my quaker babies and parrotlets that I used to raise, the bump was obvious even before they really started to feather out. I'm wondering if maybe some amazon species have a little vestigial bump there that the yellow heads lack?Melissa