I called a local parrot shop "A parrots cove" and I was told that baby caiques are extreme cry baby's naturally. And that they will keep bobbing for food even when their crop is full. Seems like a behavioral issue to me. We both might be wrong but that's the advice he told me. Of course I explained to him how I'm feeding him 3 times a day 15 ml each time etc.
As I said in my other post don't feed too much at one feeding. 15 ml it good at his current weight. Try adding one more feeding.
5 week old babies do not generally have "behavior problems". Baby birds are acting out of instint and communicating their needs much like a human baby does.
If you have a thermometer I would add that to the side of the tank at about the same height as the baby is located and you could cover the top about 80% to prevent heat from escaping. That way the heat will build up and warm up the tank.
Does your babies crop empty completely of food between feedings?
I track the weight at each feeding. I use syringes to measure the formula but you can weigh the baby before feeding and after, just write it down. In a few days you will have useful history. If all goes well then it is interesting and helpful. If you run into trouble then it will give you information which could be lifesaving. My friend who raises cockatiels and cockatoos and worked nearly 30 years in various jobs at a bird vet taught me the importance of tracking their food intake via weight.
