I wear camo under my orange vest and hat, but it's only because my camo bibs and double coat are the warmest clothes I own. Thinsulate with the latest generation of the soft, quiet, (but burr and thorn collecting) Gortex is the best I've ever owned. If it's really cold, I wear long under wear. I sprung for the cost of the warmest base layer of Under Armour, but for the price it's disappointing. I can't tell that it has anything going for it that my 15 dollar set from Costco does, warmth wise, and I don't like the wet suit fit of Under Armour. It's actually open around the wrist. My cheapos from China bothered to put elastic around the wrist.
One of the best Christmas gifts I ever got was a pair of those Gortex camo mittens with a zipper pouch on the back of the hand to load a chemical hand warmer. When you need your fingers, a quick swipe and your fingers are free through the slot in the palm, while a magnet holds the folded glove back against the top of the hand. When it's truly cold, I'm more likely to forget my gun than leave these back at the truck.
Concealing your movement, or not moving seems to be key. This is true for everything you hunt. It's the same for them as it is for us. With experience, you've already learned that it's easy to miss deer standing motionless in the wood's shadows, and they're not wearing camo. But they're easy to see if they're moving along, even in near darkness. Sometimes it doesn't seem to matter; I couldn't begin to count the number of ducks I've killed while a lab or chessie has come bounding through the water back to the blind. For some reason, that seems to work as well as any set of decoys. And sometimes deer just aren't paying attention. I've swatted a deer on the butt with the fletch end of an arrow. Another time I was preparing to leave my stand when a buck walked in. I rushed to hoist my gun back up with the rope as he watched me do it. Then I chambered a round and dropped him. Otherwise, movement is the deal breaker.
I've become a fan of enclosed deer stands for the concealment factor. If I spot a deer coming in, I can drop down, size them up, and ease into position without them noticing. Even when they've caught the movement of my hat over the edge, I don't look much different than a big red squirrel fidgeting on a limb. I've yet to spook a deer while moving around in this stand, and I've had several deer bed down right below me. While scrunched down, I've even poked a camera over the edge to shoot pics while looking up at the view finder screen. I call it the digital periscope maneuver
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