I recommend hand rearing formula called "Exact" - its made by Kaytee and is available in most large pet stores. You can also order it over the internet at
www.birds2grow.com or most other online shopping spots for pets and birds.
There are some important things to know before you start feeding.
(1) Temperature above 105 degrees when the baby recieves it: best temp range is above 105 degrees and you can test this on your arm or cheek. Your body temp is about 99 degrees, so it should feel warm to you. It will cool quickly, so be careful not to let it cool too much.
(2) Thickness - Powder/water ratio is somewhat trial and error at first. You want to have it be liquid-like in nature, not sticky. Because your baby is not a newborn, it may be a little thicker than what we would see as watery, but let it sit a few moments before feeding to make sure it won't thicken once your baby has swallowed it.
(3) Always mix a fresh batch! Like Mavis mentoned, its important to throw away all leftovers from each feeding.
So, mix a small cup of it with very hot water (water cools quickly, so best to start out hot), keeping the consistancy very liquid-like and not thick. Let it sit for a couple of minutes before feeding it to your bird because you want to make sure it doesn't thicken too much. Using an eyedropper (syringe is okay but its easy to shoot too much in your bird's mouth and he may end up aspirating - getting it into his lungs). Just a little bit each time. Leave him hungry enough to still beg but not be desperately begging. Since he is not a newborn, then you can spread the feeding times out a bit more than 2 hours - you can go with 3 to even 6 hours at night if he seems to take to it well. I do not know what kind of finches you have - if you have an African finch, there are some extra things to do to get more protein into the baby. If the parents don't mind, you can feed him and allow them to continue the other parenting duties. This usually only works with Society and Zebra finches, though.
Feel free to send me an email if you have any more questions and let us all know how it goes! As Mavis pointed out, there is a good chance he was the last to hatch and that he is a few days younger than the others. I would encourage you to watch closely - provide lots of chopped up hard-boiled egg mixed with eggfood powder and seeds so that the parents feed the babies a high protein diet and do not have trouble with calcium and vitamin D3 deficiencies. If the parents are still feeding, try not to interrupt them.
Congrats on all your little ones!
