After you have kept quail for a few days you will start to be able to tell if they are having an off day. They should have bright eyes and not be hunched or fluffed up. Their legs should be clean and smooth and they should be active and lively.
Lice and Mites
You can check for lice and mites by looking at the skin and under the wings. Lice or mites can cause otherwise healthy quail to lose feathers, weight and cause a drop in egg production. You can treat them with a small amount of anti-mite powder. However prevention is possible by using replacing bedding frequently and keeping the house clean.
You should keep an eye on your quails dropping. You should look out for constantly loose or odd coloured droppings.
Checking the vent
As with chickens you should check that the vent is moist and white, with no lumps or crustiness.
The birds vary in weight according to breed but they should feel plump in the hand and the breast bone should not jut out.
Quail are generally very hardy but should they acquire any serious ailment it is best to have them put to sleep as there is only a limited amount of medication licensed for quail and even fewer vets who have a clue about quail illnesses.