Old birds handle it much better which makes it much harder to nip in the bud. Loss of appetite, loss of condition, no desire to exercise are the things to look out for. When handling their crop will feel spongy and the pigeon itself feels warmer in the hand than it usually would (akin to running a fever). If peeps were to look at y/b/s as the equivalent of us having a bout of the flu they wouldn't be far of the mark, Its not as scary neither if you look at it like this. In the main when we go down with a bout of flu we lose our appetite, have no desire to work, feel like crap, run a fever & maybe vomit. Doctors orders would be to rest........... and that goes the same for our pigeons. A bit of subject I know but some look at y/b/s as a taboo when there's no need to.