Aldus is at the stage (according to a book) where he is making more saliva but has not yet figured out the swallowing trick. You see him here in a bib. The bib is also nice because he recently has started to spit up/burp up more of his food. This is a bit strange as he did not spit up much at all before and has started to spit up interesting large amounts in one burp (no it is not so much that he requires medical attention, it is just impressive to see) (really). And sometimes, he will not burp but have a longer slow release of milk/spit/stuff. It is sort of like the difference between Pahoehoe and A'a. Except that his spit is not coming out at several hundered degrees with smoke and fire.

But, like all babies, a good burp after eating will leave him in the mood to sleep.