I don't seem to have a problem with uploading and increasing sharpness, it's usually the other way round and degrading the photos on here.
You have some very nice captures of the BT, but to me, they do look over processed. Whats your typical PP workflow for birds, as I find oversharpening and upping the clarity, vibrance and saturation sliders makes the birds look un-natuaral and increases artifacts / noise etc........
Here's a couple of recent BT from me and they look flatter than your photos, so not sure whats happening with you?..... Export settings possibly?
Blue Tit with Nikon D810 by
Swansea Jack, on Flickr
Blue Tit with Nikon D810 by
Swansea Jack, on Flickr