The following comments were authored by Dr. Greg Burkett, Board Certified Avian Veterinarian

"Most bacteria come from water dishes.  The most common bacterial infection from water is Pseudomonas.  Pseudomonas is a common cause of feather damaging behaviors (editor: among other problems) . If you are not changing your water bowls every three hours, then I guarantee that your dishes contain significant amounts of bacteria.  Want proof?  Feel the bottom of the bowl the next time you wash it and discover the slime on the bottom.  This is called a biofilm and it is a bed of bacteria.  The numbers of bacteria in this biofilm double every three hours.  Every time your bird drinks from this dirty bowl he ingests bacteria.  The best prevention for this is to put your bird on a water bottle.  Change the bottle once daily and check it 2-3 times daily to be sure it is working."