So, Both birdfolk and gryphons have a head structure, similar to that of birds of prey, i.e: forward facing eyes. Sure, the color of the plumage and the beak-type can vary, but one problem is still present.
While gryphon and birdfolk character often express anger, I don't want them to look grumpy all the time. Would it be good for comedy? Sure, but I hate fun.
As you can see, dragons have flexible skin and possibly extra muscles underneath, that could be contracted or relaxed, allowing for the creation of complex "facial" expressions. Avians, on the other hand, have a rigid beak.
How could I give gryphons and birdfolk facial expression without removing the beak or turning them into horrifying monsters?