Other than canker, respiratory infections are probably the most feared type of problem that pigeon owners face. Respiratory infections are extremely contagious and stressed, older, and younger birds are most susceptible to infection.
Respiratory infections make it hard for a bird to breathe and fly so they are less active and competing pigeons will perform poorly. If left untreated, a pigeon with a respiratory infection will be open mouth breathing, have an increased effort while breathing, sit fluffed up with their eyes closed, not eat, and will ultimately die.
Many things can cause a respiratory infection in a pigeon including fungi, viruses, bacteria, and mites. The infections can involve the lungs, air sacs, sinuses and other parts of the respiratory tract. There may be visible discharge from the nares, inside the mouth or choana, or you may actually hear your pigeon sneezing and/or coughing if they have a respiratory infection. Aggressive treatment, including environmental cleaning, treating underlying parasites that may have predisposed your pigeon to getting sick, finding the cause of the infection and medicating your pigeon, are all important in eradicating a respiratory infection.