1. Draw a guy.
2. Add a beard.
3. Draw a bird in the beard.
Another way is to have some really weird dudes visit you as you sketch them and their strange beard ecosystems. I speak from experience when I say, “Live models are a huge mistake! Bird poop everywhere! I’m missing my left thumb now! And those prima-dona beardos with their holier than thou attitudes? No, just make this stuff up. It’s better that way.”
After eighteen years of sweat, tears, and bird poop, at least I got a good coloring book out of it.