There are two types of snuffly chickens that I have experienced.
There are snuffly chickens who snuffle but still eat, roost, scratch, peck, roll in the dirt (not now, no dirt!)and in every other way act as they normally do. Those snuffy birds, I leave alone.
If a bird is sick, hunched, head down, feathers ruffled, standing away from the other birds, not eating, not moving THAT is cause for alarm. THat is a sick bord and should be separated from the flock immediately.
If your birds look sick and have nasal discharge that STINKS (yes, you will smell it!) consider coryza. Not much you can do. Separate or cull.
If your coop is closed up tight to keep heat in, you may create a dusty, humid atmosphere that sets your birds up for respiratory problems. If you have not shovelled out the poop and the ammonia levels in the air are high, you are irritating your birds sinuses, eyes and other mucous membranes. SO get some fresh air circulating and shovel out the poo! Their environment can be the cause of the problem, may not be a 'germ'.
I do not treat my birds with antibiotics for run-of-the-mill snuffles. If they do not look and act sick, I let their immune system fight it out. YOu will have stronger chickens for it! BUt if you have SICK birds, more steps will be required. Observing the behaviour of your birds when they are healthy will aid you greatly in recognizing a change in behaviour that tells you when they are sick. Good luck!
