My Budgie is Not Acting Normal. Is He Sick?

Signs of illness include:

Change in droppings: watery or loose, change in color.
Feathers fluffed up constantly, especially on the back between the wings (this is one of the most important signs that a budgie is seriously ill).
Heavy discoloration on feathers above the nostrils and/or excessive sneezing (possible respiratory infection)
Vomiting (seeds, or slimy clear stuff on feathers around face)
Seeds in their droppings
Change in temperament, listlessness, or quietness in a normally active budgie.
Not eating.
Eating much more than usual.

If you have noticed that something seems not quite right about your budgie, and he is exhibiting one or more of the above signs, you should make an appointment with an avian vet ASAP. You can determine they are an avian vet by asking specifically "Are you an avian specialist?" Just because a vet "sees birds" does not make them an avian specialist. You can use http://aav.org/vet-lookup/ to help you look up an avian vet in your area.

In the meantime, you can cover the cage on the top and 3 sides, and put a heating pad under 1/2 the cage to keep him warm (it is difficult for a budgie to maintain its body heat when seriously ill). Make sure he has plenty of water within reach. If he is on the floor of the cage, put a dish of water on the floor for easy access.