Normal bird feathers develop in the feather follicles in the layer of skin known as the dermis, compared to the fur of mammals which grows from hair follicles.
All birds can develop feather cysts, but canaries are known to have them more frequently. A feather cyst is an accumulation of keratin and feather material under the skin that occurs when the growing feather is unable to protrude through its natural opening in the skin, and curls up within the follicle. The feather continues to grow under the skin, increasing the accumulation of keratin, and creating inflammation around the follicle, sometimes causing the cyst to rupture. Feather cysts appear as an oval, yellow-white swelling, visible under the transparent layer of skin and can involve one or more follicles. Feather cysts are commonly found along the borders of the wings involving the primary feathers. Large feather cysts can sometimes be found on the body of the bird as well.
Large feather cyst on the body of a canary
Feather cysts may be caused by a malformation or trauma to the follicle, a viral or bacterial infection, plucking, or inadequate nutrition. A genetic condition seems to be the cause in canaries, particularly in the Gloucester or Norwhich canary. These breeds have an inherited predisposition to developing feather cysts due to their soft duvet of feathers, and cysts may occur throughout their lives.
The treatment of feather cysts relies on a fast diagnosis and the skills of a veterinarian familiar with avian medicine. A small cyst can sometimes be manually emptied of its contents, but if the cyst is infected, a result of plucking, or the size is too large, a surgical excision is required. In most cases, the wound will be closed by sutures, but occasionally the contents will be removed and the cyst will be left open, particularly if the location of the cyst is the border of the wing, where the skin is very thin. There is, therefore, a strong possibility that another cyst will develop in the same area, despite the surgical resection of the primary cyst.
Clustered feather cyst on a canary.
Surgical wound after the excision of a large feather cyst.
Surgical wound after the excision of a clustered feather cyst.