My wife came across this chart. I have not seen it posted before on the forum so I thought I would post the link. It looks like there is some good information here.
http://www.welphatchery.com/poultry_health.asp
We found our rooster, Cogburn (I know, I know) dead in the run on Friday. He was a 5 1/2 month old Buff Orp. He has been doing just fine with no obvious signs of any problems. We had noticed that over the past week of so he had been shaking his head from time to time but we could find nothing...