Why did my budgie chicks die in the nest box? Heat, feeding, or smell?

Keep the nest box clean. You can gently scoop the chicks up in a paper towel, clean the box, add clean nesting material and return the chicks. Make sure Noshi is eating a healthy. Ideally, she should be eating a commercial pelleted diet such as Exact or Pretty Bird. You can supplement with a fortified seed mix and fresh fruits and vegetables. Monitor the chicks for full crops (which means they are being fed) and weight gain. If necessary, a commercial hand feeding formula can be used to supplement the chicks.

It could be infection, congenital defects, environmental issues (too cold) simply parental inexperience. Post mortem exams and diagnostics on the chicks may provide an answer. It is difficult to determine cause from an image. Consider giving the hen a rest from breeding. Clean and sanitize the cage, bowls, toys and perches. Discard anything that cannot be sanitized. Clean and sanitize the nesting boxes or replace them entirely. Speak with local breeders to determine if this is not an isolated issue. They may also be able to provide helpful tips or insight.

You should have the chicks or parents examined by your veterinarian or an experienced avian vet. A culture may identify bacteria. If you are hand feeding, use fresh food for each clutch. Clean and sanitize all equipment between feedings or clutches. Clean and sanitize all cages, bowls, toys nest boxes and perches. Discard anything that cannot be sanitized. Change cage paper daily. Make sure the chicks are kept warm and are emptying their crops regularly. Sour crop, or crop stasis, can result in a hard crop full of spoiled food and bacteria or fungi. This can kill young chicks if left untreated.

It would be hard to tell what caused the babies to die without a necropsy/examination. It's possible there was a genetic issue, an illness, or the babies were just weak/not fed as well and so passed on. Your parents are a bit young still and may be having trouble caring for all the babies, so helping out by supplementing with baby bird food may be best to help the remaining babies thrive.

As long as the parents are taking care of the hatchling themselves, you shouldn't need to do anything as they will keep it warm by laying with it in the nest, and feed it as needed. It also seems like you are feeding lots of nutrition-filled items to your birds as well! It is a good idea to have some baby bird food and a syringe on hand that you can mix up if you need to help with feeding, or if the parents aren't caring for it. Most pet stores carry this and will have feeding instructions on the side of the bag. Congrats on the baby bird! It sounds like it and its parents are in good hands.

Yes, you may move them without consequence. Gently scoop them up with a bit of nesting material and place them in the larger nest box. Your hen may complain, but she will settle down once she is back with her chicks.

Momma bird may be a bit stressed out now that there are new babies to care for. Adding in extra food and water dishes so that each bird has one to eat at without fighting, and making sure both birds have their own perches to relax on can help reduce tension. As for the babies, momma bird should care for them herself, however having some commercial baby bird food (most pet stores will carry it) can be useful in case she can't care for them all on her own. As they get a bit older and start to explore, you can start to offer treats and pets to get them used to being handled.