As is the case with all animals, good health will require a good diet, stress-free environments and plenty of warmth/ no harsh conditions. Even with all these boxes ticked, your finches can still fall ill.

A change in your pet bird's behaviour or appearance could be rooted in illness
Spotting a Sick Finch
Drastic behavioral changes will be the first sign that your bird(s) is coming down with something. A normally lively and active bird will become lethargic and will sit quietly on a perch taking little interest in what’s going on around them. The posture of your bird will also be a dead giveaway. A tucked back head “behind the wing”, a change in posture or drooping tail or wings, fluffed up feathers, half closed eyes, panting or sitting on the cage floor are all signs of an illness. Loose or discolored droppings as well as a messy vent or stains along the breast feathers are also signs.
Treating a Sick Finch
Once you have identified a bird as ill, you will need to act quickly. A spare cage will also come in handy as a form of isolation from any other birds. Birds that live alone can of course stay in their cages.
Once certain that your bird is ill, a trip to the vets will be needed asap as illness in small creatures such as finches can lead to death at an alarming rate. Place a heat lamp near the cage of the ill bird, as sick birds are unable to maintain proper body temperatures. Place food and water in the cage too, even if your bird shows no interest in the food. You can tempt them to eat at least a little bit with more appetising food such as mealworms and berries.
Don’t act prematurely and try to cure an illness unless you are sure what it is. Some ailments will be much more obvious than others. The following pages will provide a list of the more common ailments that can fall upon your finches.
Trudi, 24 July 2021
Hi ive found your writting and advice very useful ,I have recently bought 3 budgies and 2 canaries they came in the same cage and get along really well .