The lower extremity of the face below the mouth; the point of the under jaw.

The exterior or under surface embraced between the branches of the lower jaw bone, in birds.

Under bill

The chin is the area just beneath the bill, above the throat. It is relatively small on most birds, but some put it to good use. Blue jays, for instance, have lots of feathers at the base of their beak and on their chin as well. These feathers come in handy many a time when searching for the perfect seed in a pile and thrashing the bad ones away. I've been annoyed many times when blue jays do this, shoveling huge groups of sunflower seeds off onto the ground to find the right one somewhere deep in the pile. Of course, the chin isn't completely useless for identification either, to get back on the subject. Ravens are discernable from crows virtually only by their slightly larger size and shaggy throat / chin feathers.

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