Budgie feathers puffed up ?

Fluffing up feathers once in a while is normal for budgies. Budgies will fluff up their feathers to preen or release tension. If your budgie has them fluffed up often, this is a sign of illness. Budgies fluff up their feathers to maintain their body temperature and stay warm. Budgies will breathe harder when flying or exercising. That is normal. If they breathe with an open-mouthed beak, this is a sign of a serious illness. Time to take the budgie to an avian vet.

Nothing to worry about! I have a 6 month old male yellow budgie. They just do it as they may feel a tickle or somthing. If it happens commonly there may be somthing worrying for you. A moult! Prepare for the endless feathers on the floor! Moults happenevery 3 months my budgie has nearly finished his second!

budgies usually puff up them selves to intimidate other birds and they also tend to puff up alot when they are molting. If your bird was ill, there are probably other symptoms too so I rule out illness. However, they may be cold. I recommend you check the temperature with a thermometer when you notice they fluff themselves up.In this case, I sugest you raise the temperature or if you dont have a thermostat, simply throw a blanket over the cage. I wouldn't worry about this too much because I have budgies of my own and they always do this.

Is he perching on one foot or two?

Usually, a sick bird will not have the balance to perch on one foot.

All birds sit with their feathers puffed up- its how they keep warm (and why they do it when they are sick)

however, if he is perching on one foot he is probably fine.

If you do notice any other problems, like diarrheah, not eating, etc, then you should consult a vet.