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Chapter 18

The Head

III NORMAL ANATOMY

filter-equipped tongues to remove nutrients from the
The typical bird head is composed of a beak (or bottoms of wetlands, lakes, and rivers or, if the oppor-
bill), the upper part of which contains the nostrils tunity (or necessity) arises, to graze the nearby
and tongue; a facial region dominated by the eyes; shorelines.
and a cranium. All but the beak are covered in
feathers.
The Tongue
As in the case of the beak, the design of the tongue

III BEAK AND TONGUE: AN reflects the diet. Geese and ducks have tongues

ANATOMICAL PERSPECTIVE designed to filter the bottom material on which
they feed (Figure 18-11). Raptors possess a short thick

muscular tongue that propels chunks of flesh back into
The Beak
the throat to be subsequently swallowed (Figure
Enormous variability exists in the heads of birds, espe- 18-12).
cially in beaks, which for the most part refl ect their Woodpeckers, the anteaters of the bird world, have
individual diets. For example, the enormous sharply an extremely long tongue, thin as a pencil lead, that is
hooked beak of the bald eagle is capable of fl aying capable of extending well beyond the tip of the beak
flesh from bone as if it were paper (Figure 18-1), or the in search of insects (Figure 18-13). Parrots have a par-

powerful brutish beak of a parrot is able to crack a ticularly dexterous tongue that is guided by the rostral
Brazil nut as easily as it might a grape (Figure 18-2). elements of the hyoid system, a pair of bony structures
Other variants include the long gracefully curved embedded in the tongue, the entoglossum bones (Figure
beak of a flicker, which is designed to extract insects 18-14).

from deep beneath the bark of trees (Figure 18-3), or
the pikelike beak of a jay (Figure 18-4), which is capable
of grasping a peanut, puncturing its shell, and with- III THE JAWS, FACIAL REGION, AND
drawing its content, all within a few moments. Even CRANIUM: A RADIOGRAPHIC
the small stout triangular beak of the sparrow has been PERSPECTIVE

optimized for the task of finding seed whether in the
urban canyons or the great boreal forests (Figure Jaws, Nasal Cavities, and
18-5). Paranasal Sinuses
The beaks of water birds are equally varied, ranging
from the expandable pouch of a pelican (Figures 18-6 Unlike mammals, many birds have dynamic jaws that
and 18-7) to the raptor-like hook of a cormorant (Figure achieve maximal opening either by a system of adjust-
18-8). Ducks (Figure 18-9) and geese (Figure 18-10) able bony levers and pivot points, or in the case of

possess broad flat beaks that resemble the blade of an psittacines, by a jointed beak, termed the craniofacial
inverted shovel; these work in conjunction with their Text continued on p. 189.
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