If you used a 'medicinal' canker product on your birds, chances are that it will have some side effect. For example, Flagyl is an antimicrobial for humans, that is also given to the birds to 'canker' them. 2 of our members were ill and put on a Flagyl drip in hospital . Both of them described feeling very weak after the Flagyl treatment. It is maybe a similar side effect that you are seeing in your birds.
On the thirst bit: there is a lot of misinformation (or misunderstanding) about electrolytes (salts & sugars in balance). These are designed primarily for human athletes, and we humans sweat during exercise, lose salts and that creates an imbalance which drinking electrolytes restores.
Pigeons are athletes too, but they don't sweat, they don't lose salts (they keep them in the blood to regulate body heat in flight) what they lose is water - lots of it, and that creates a water / salt imbalance, too little water and too much salt - which drinking water restores. It is reckoned a bird coming home from a race given free access to all the water it needs is fully rehydrated within 30 minutes. |