Failure to Thrive

Are your baby finches dying shortly after leaving the nest even though their parents are feeding them? If they just can't seem to gain weight and appear to getting weaker we call it Failure to Thrive. The term is actually a very general one used when the exact cause of the illness isn't known. With young finches that die in the nest it isn't easy to notice changes in their health. Many die before they leave the nest. It's in the few that survive just long enough to fledge that we usually see the problem.
These chicks are often weak, small, under weight, and inactive except for begging for food. If you hold one in your hand you will notice the breastbone is sticking out quite a bit. It's a large V shaped bone on the breast, pretty easy to feel in underweight finches. When chicks are suffering from this the cause can usually be traced directly back to the parent finches.
This condition can also occur in adult finches just as easily as it can in chicks. However when an adult finch starts getting weak and losing weight it's usually referred to as Going Light. It's not as common in adults as it is in chicks. Chicks don't have their immune systems built up, nor are they prepared to deal with parasites. Adults on the other hand tend to have a better chance of surviving and thriving once again.
There are several possible causes for this condition. They are both the same for the young and their parents. Let's go through the list shall we:

1. Bacteria – This is number one on the list because it's the most common. There are several types of bacteria can cause the symptoms, thankfully the treatment is pretty simple. Tetratex works well but it can only be given to the adult finches. They in turn give it to their chicks while feeding them. Usually the parents already had the bacteria in their systems but their immune systems were able to prevent illness. They passed the bacteria on to their chicks when feeding them and the chicks don't have a sufficient immune system to fight off the bacteria invaders. Antibiotics should always be followed with a Probiotic to reestablish the health bacteria of the digestive tract.
2. Avian Gastric Yeast – Also known as Megabacteria. It isn’t a bacteria and will not be effected by the use of antibiotics. Your vet can test for this pathogen and prescribe the correct medication. 
3. Protozoa – Now we have the second most common cause. Like the bacteria it's given to the chicks by their parents. The treatment is Ronivet-S or Ronex, given in the drinking water of the parents. They in turn give the medication to their young. Also like the bacteria it's highly possible the parents aren't showing any signs of the protozoal infection.
4. Coccidiosis - This is actually a protozoa but these protozoa are much more difficult to kill than the other types. A special medication called Cocci-Care was developed to deal specifically with these protozoa.
5. Parasites – These you can usually spot, but not always. If the parasites are worms you may see signs of them in the finches droppings or in the chicks mouths. Treat them with Worm Away. However, more common than worms is blood sucking ticks or mites. These little pests are most common in outdoor aviaries. They sneak in under the cover of night and cause a lot of harm. You won't usually see the bugs unless they have set up a home inside a finch's nest. The warm, humid and food filled nest is a haven for these bugs. When parasites are to blame this may be the only time you'll see the symptoms in both the parents and the chicks. Treat the finches, cage, and area with a misting of Avian Insect Liquidator. Finally we have air sac mites and scaly face mites who can do equal harm to chicks and parents. For these two types of mites you need to treat the parents with Iverlux.
6. Genetic – This one is common and less mysterious than the other three I've talked about. Inbreeding can play a major roll here and we all know how much I don't encourage inbreeding. This is just one of the reasons why. Sometimes inbreeding isn't at fault however it can also just be a bad combination of genes. When genetics are the cause there is nothing you can do for the chicks. They will adapt or die, death being the usual result. Quite often they simply have poorly developed organs and lack the ability to digest properly. Other times it's an inability to properly remove waste material from the body even though the finch is pooping. When genetics does play a role the entire clutch usually dies, if some do survive they tend to me small and sickly. The only thing you can do is try a new pairing with new mates.