I have 3 baby budgies in one nest. 1 fledged yesterday, 1 is about to, but the youngest is skinny and fluffed up tonight, but was fine this morning. Any idea what could be wrong? They are in the outdoor aviary and its getting colder, so I'm thinking maybe thats the problem? I'm going to go out now and bring the little one inside for the night to keep an eye on him and keep him warm.

Can you be sure that this baby has been fed properly by it's parents . Sometimes the older and bigger babies get the lions share of the food. Is there food in its crop ? Can you give it a supplementary feed ?

Well after a night inside bub appears fine! Maybe it was just the cold. He had been fed- he was just fed when I brought him inside last night. I've just put him back in the nest as it's warmer now, and will see how he goes.