Anatomical Directions, as described in “Handbook of Bird Biology“ (2004): Researchers use specific terms to refer unambiguously to directions and relative locations on the bodies of animals, as illustrated here. Toward the back is termed dorsal, and toward the belly is ventral; toward the midline of the body is medial, toward the side is lateral, and something positioned on the midline of the body is median; toward the center of the body is proximal, and away from the center is distal. To describe directions toward the head or tail, cranial and caudal are generally used, respectively; but anterior and posterior may be used as well, although their use is sometimes limited to sites within the inner ear and eye. To refer to something in the direction of the tip of the beak, from a point of reference on the head, the term rostral is used. The terms left and right refer to the animal's own left and right, not those of the observer. It is also useful, for certain anatomical sectional views, to refer to planes cut through an animal. For a bird in the position illustrated, a sagittal plane extends vertically from head to tail, a transverse plane extends vertically from side to side, and a frontal plane extends horizontally.

My diagram is based on illustrations and terms from:

Proctor, NS and PJ Lynch. 1993. Manual of Ornithology: Avian Structure and Function.Yale University Press.

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Podulka, S., R. W. Rohrbaugh Jr. & R. Bonney (eds.). 2004. Handbook of Bird Biology.The Cornell Lab of Ornithology.

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