if sound crackly then you'l need to treat , it sounds like your birds have ample room and it maybe the bedding giving off toxic fumes which will poison the birds or ventilation needs improving perhaps a few photos of yer loft and dusting the deep litter with lime will help dry droppings quicker and remove the amonnia from the loft
sounds like respiratry youve got air going straight through and not in at bottom of front of loft ? if you put you ear under wing you can here its lungs inflate deflate and you'l get a rough idea if alls not well when did you change your bedding ? is there any ammonia smell in the loft ?
its usualy a vitamin deficency along with a draught dont have draughts and ensure you suply vitamins , one eye cold can sometimes get confused with Hexamitiasis
heres a good site for you to look at pigeon ailments , a good avian vet is worth there weight in gold and you should seek one out in your area so can regulary test your birds to help maintain there health :
http://www.chevita.com/en/pigeons/symptoms/index.php
as pms are working and issues have been resolved i shall now lock this topic , many thanks for your cooperation and understanding whilst these problems were being resolved Regards Mark
it could well be respiritary althought its treatable the only way to get rid is to ensure your loft has good ventilation and is not over crowded when did you canker last ?
could be dust , normal preening , canker , one eye cold , a draught, but without knowing or seeing your loft then very hard to get every aspect taken into consideration
yes bops are about all year round the racing season is 6 months so if locked up best part of it thats 50% less birds losted , if bops kill and are successfull they'll keep returning as long as the food source is there if locked up no food source then they'll move on
why let them out during winter ? i keep mine in from end of racing till i've finished breeding , seems your just a free food outlet to passing bops , at least if locked up your starving the local bops and they'll look elsewheres for food