I believe that there are a few essentials that should be in every upland bird hunters pack. (Assuming that you are hunting with a dog)
Starting with the most obvious:

*Shot Shells
*Cell Phone (if it might works in the area)
*Whatever electronics you use for your dogs (e-collars, tracking systems)
*A snack
*Water (for yourself)
*Plenty of water for the dog(s)
*A light wind breaker (I have one designed for running that weighs practically nothing that I keep in my pack at all times. You never know when conditions might change and you will be happy to have it.)
*A light pair of Gloves
*A Fleece Beanie
*A set of dog boots for each dog (this way your dog should never really get foot sore)
*Extra Whistle (I don’t know how many times I have forgotten my main whistle and had to use my back up)
*Extra batteries for your tracking system
*A Leatherman Tool (the knife comes in handy, but the pliers are essential for removing cactus, quills, or whatever object you will find sticking out of your dog from time to time.)
*Duct Tape
*Goss
*Q-Tips (for seeds, dirt, or whatever needs to be removed from your dogs eyes)
*Benadryl (for bites, or stings) (talk to your veterinarian about how much would be appropriate for you dog)
*EMT Gel (it can quickly and easily fill up and seal off small cuts and scrapes, keeping them clean and sanitized until the end of your hunt)

I generally don’t carry much more than that. As for dog first aid, I keep a complete kit back at the truck. Fixing small cuts can usually be done easily with Super Glue. I usually don’t carry Super Glue with me, though it is not a bad idea, but I kind of figure that anything small enough to be glued can wait until we are done hunting (cover in EMT Gel), and will likely need to be cleaned anyway. And anything too big for super glue, depending on the location, will probably mean the end of the days hunt. The Goss and Duct Tape can help with that until I am back at the truck, or at the Veterinarians.

Obviously, the kind of hunting that you are doing, the kind of dogs that you run, the number of dogs you are running, the terrain that you are hunting, personal preference, and weather conditions are all factors in what you will add to your pack. If you have a good hunting pack that will put the weight on your hips, and there now are some good ones out there, the small amount of added weight will be no big deal.