Birds and worms – What’s the difference between Roundworm, Tapeworm, Hairworm, Threadworm? 
Roundworm
Live in the intestine of a bird. They are white and are normally 1 inch to 1½ inches long (3 cm to 4 cm), although they can be up to 4 inches (10 cm). Roundworm are easily spotted if passed in your bird’s droppings. Being a parasite, roundworm live and eat off their host, ie your pet bird! Out in the air and away from the host they die and shrivel to a pink color.
Roundworm eggs are passed in a bird’s droppings, then passed from bird to bird as they come into contact with these infected droppings.
Signs of Roundworm
The bird eats a lot but loses weight due to the roundworm absorbing all the available nutrients. It has slightly ruffled feathers and poor feather condition, picking or scratching at the stomach area, disinterested in its surroundings, messy vent, diarrhea or straining to pass droppings if infested heavily (a severe blockage can lead to death), and poor development in young birds.
Threadworm
Fine and threadlike living in the esophagus, crop or intestine. There are many types ranging in length from ¼ inch to 2½ inches (1 cm to 6 cm). Threadworm are also known as Hairworm.
Threadworm eggs are passed in a bird’s droppings, then passed from bird to bird as they come into contact with these infected droppings.
Signs of Threadworm
Loss of appetite, weight loss, anemia, disinterested in its surroundings, vomiting, diarrhea with blood in it, death.
Tapeworm
Affix to the wall of the intestine and vary in type and length, ranging from less than ¼ inch to 12 inches (1 cm to 30 cm).
Tapeworm eggs are passed in a bird’s droppings, then eaten by small insects such as snails and beetles. Birds then eat the insects. For this reason, tapeworm are more commonly found in insect eating birds, rather than seedeaters.
Signs of Tapeworm
Loss of appetite, weight loss, anemia, droppings contain mucus or bits of tapeworm.