For the sort of country seen in the photos I would be at home in shorts and fleece shirts, long or short sleeve. Add on long sleeved and long legged thermals under the top layers and you will be good to go in colder weather. I now wear light synthetic hunting boots with good woollen socks for most of my hunting unless it is real alpine snow work. Light boots are much more agile and dry out quickly if they get wet. Top these off with long fleece style gaiters (I use Markhor brand, water proof, quiet and do not get too hot). If long pants are wanted then you can't beat the lightness, warmth and overall comfort of fleece track pants, hunting green or camo, and combined with gaiters will stay dry in long wet grass. Like leather boots, my heavy water proof hunting trousers are reserved for extreme cold and wet in the Alps.

Fleece clothing and synthetic boots just can't be beat for versatility and comfort today and as NitroX points out, can be layered to provide the comfort level required.

Whether this satisfies the custom who really cares, I dress to hunt in comfort not to impress or satisfy some perceived quaint custom that's most likely long outdated.

As to shorts, well the Scots are pretty famous for their tartan 'skirt' aren't they? It all comes down to what's underneath!!!!!!