The 4 different types of conures that I have hand fed have all done the same. 
Speceally withing the last 3 weeks before weaning. Frome these birds the suns 
were the ones that did it the most. In my opinion, if the formula is warm 
enough, and the bird does this, then there is no way of stoping it.
Mayby their maternal instincs of regurgitating food kiks in on babies being
fed soft foods. My scarlet macaw would feed me a seed everyonce in a while
even after fully weaned. I think that this is something unliked that simply
comes with the job. I would feed my babies, wait half an hour, then wipe them 
with a wet towel or in extreme cases give them a warm bath.  
 
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