| There is a great article by Margaret A. Wissman, DVM on Bird Feet Health which can be found at Bird Chanel.com and if you have any concerns your first port of call should always be your Avian Vet.
"Take The Pressure Off Your Bird’s Feet (this is just a snippet) Birds need a variety of perches of differing diameters and textures for optimal foot health. Because of the locking mechanism found in the bird’s foot, they can develop pressure points on the bottoms of the feet from constantly standing on perches of the same diameter. (Bumblefoot is used as an all-encompassing term for issues involving infection or inflammation of the foot.) Over time, this can develop into pressure sores, called pododermatitis. Sores can then become infected, resulting in deep lesions that can be very difficult to cure".
By ensuring that your parrot (regardless of their size) has a variety of diameters and textures available to perch on you are at least eliminating one of the common causes of Bumblefoot. Of course there are factors other than incorrect or inadequate perching to take into account, which is why it is so important to consult with your Avian Vet. In our opinion there is no incorrect perch size as long as you have a good balance of diameters (relevant to your birds size) and it is always best to err on the large side rather than the small side. In the case of the 3 little birds we recently helped, two Budgies and a Finch, it was just the perching that was found to be the problem and because their owners were quick to notice something was amiss with their normal perching habits, a visit to the vets, some medication and a change of perches had them back to their usual happy selves in no time. The perches in question, plastic, dowel and the other was a combination of plastic with an abrasive strip down the centre, all came as standard with their varying cage types. Although we are not fans of Plastic and Dowel perching, it has to be said that if given in conjunction with other perch types they are not a problem; however we would be concerned about the abrasive strip one. They say variety is the spice of life, in the case of perching variety is essential to their wellbeing. | 
