Canaries particularly in an outdoor aviary are much more susceptible to internal parasites, which can be passed from wild birds, insects, and from bird to bird when in a single colony.
Tapeworms are generally not a common problem for the indoor pet canary unless it was infected before you got it.

Birds get tapeworms by eating an insect that is infested with tapeworms or by ingesting a tapeworm egg passed by another bird.

If your canary is losing weight, ("going light"), it would be a good idea to have an avian veterinarian look at the droppings. Under a microscope eggs will be clearly evident if your bird has a tapeworm.
Tapeworms consume nutrients from the food your bird eats. This may leave the bird malnourished and sickly and you may find your bird sitting on the cage floor.
The tapeworms will multiply until they block your birds digestive tract at this point death is not far away and there is little you can do. You may see a little blood at the vent.

It is recommended that you treat your birds particularly if housed outside, with a bird wormer which kills Tapeworm. This should be done according to instructions (which is sometimes an over kill), and at least annually.

Product Name: WORMOUT GEL (www.vetafarm.com.au)

Product Size: 50mL 100mL 250mL 1litre

Ingredients: Praziquantel, Oxfendazole

Guaranteed Analysis: Praziquantel 20g/L and Oxfendazole 20g/L

Directions: All Aviary Birds - add 1mL to 80mL of water. Supply medicated water for 2 days. Remove other sources of water during treatment. Aviaries should be treated at least four times a year.

Treatment by Crop Needle: Fill a 1mL syringe with Wormout Gel and deliver. Administer 0.05mL per 100g body weight, once. Repeat three monthly

Notes: Soluble bird wormer.
Oxfendazole and Praziquantel are the actives in Wormout Gel. They are recognised as two of the safest wormers available and their combination covers all the major worm species found in birds including Thread Worm, Tapeworm, Roundworm, Caecal Worm, and Hook Worm.

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