Macrorhabdus, also known as Avian Gastric Yeast (formerly referred to as Megabacteria), is a fungal organism that colonises the lining of

Psittacine Beak and Feather Disease (PBFD) is a very serious infection which can affect many species of parrots.

Chlamydia (Chlamydia psittaci) is a type of bacteria that is sometimes found in birds and is able to be spread from birds to people (i.e. it is zoonotic).

Knemidokoptes (more commonly known as scaly face or scaly leg mites) usually affect birds with compromised immune systems, as well as young birds.

Toxicity from heavy metals can occur when birds ingest substances that contain lead, or high amounts of zinc or copper.