Bird-demons

The many demons with bird-like features in Hieronymus Bosch's work refer to folkish proverbs of his time (the spoonbill for instance refers to gossipers, because it is a bird which drags its bill through the mud). But i am now inclined to think that there might be a connection to the creepy masks plague doctors used to wear, a century before he was born. I dhave to research if they were still in use during his life, but the memory of them must have been alive, at least. I imagine a collection of them like in the pic below in storage in a hospital could be of use in one of the still unfinished chapters of my Bosch story.