by Pajarita » Thu Feb 12, 2015 12:04 pm
Yes, three is not a good number for budgies, it needs to be four or more than six.
First thing you need to do is separate him from the other two so put him in a cage by himself, side by side the cage where the other two are so he can hear and see them but they cannot reach him. This is not only because, as Wolf said, they might be ganging up on him and preventing him from eating enough but also because sick/weak birds always do better on their own plus, this way, you will be able to see how much he eats and poops and what his poop looks like. And keep him warm (heating pad under the bottom of the cage is good).
I would not use wild or brown rice for a too skinny bird, I would use white rice, white bread and millet (mix the cooked white rice with a finch mix -they are mostly millet) because you want to fatten him up. Wolf is right that adding finely chopped veggies is the way to go with them and I would do this with the other two but I would not try to switch him to a vastly different diet now that he is so skinny, I would wait until he gains some weight. But do give him leafy greens and sweet corn (budgies love them and they need them for vitamins). If you don't feed anything but seeds, please get some good powder vitamin/mineral supplement that dilutes in water (not the one that you put on the food because you need to make sure he is getting them).
Does he have an overgrown beak or too long nails? Is his poop runny or his urates any other color other than white? Because if the answer is yes to any of these questions, he might have liver malfunction in the last stages. Have you palpated his abdomen to see if you can feel a mass in there? Budgies are very prone to tumors...