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BIRDING 101
LESSON 5: A BILL WITHOUT TEETH


The projecting jaws of a bird, with their horny sheath, are called bills, beaks, or technically, the rostrum.


Birds have no teeth but they can definitely cut food, break seeds and nuts, extract food from hard to reach places and much more. The horny covering of both the upper and lower mandible is known as the rhamphotheca. Bill shape is very important to the bird for obtaining its preferred food (and to us in identifying them).

In the bird world it is uncommon for bills of males and females of the same species to be significantly different (sexual dimorphism). However, a few Utah birds do display sexual dimorphism. Male and female American Avocets can be identified with some degree of accuracy by how much the recurved bill curves upward -- more upturned in the female. Can you guess why the scientific name of the American Avocet is Recurvirostra americana? Another example is the White Pelican where males grow an erect horny plate on the top of the bill during breeding season.

By understanding the adaptations of the bill in relation to a bird's feeding habits, birders can easily place birds into groups to facilitate identification. The long pointed bills of herons and egrets are designed to seize fast moving prey in shallow water and reeds. A more perfected bill for grasping fish in open water is the bill of the merganser,

with its saw-tooth-like lateral cutting edges (tomia). The elongated, slender bills of most wading birds (shorebirds) are adapted to probing for food in mud or sand. We could go on and on -- the "toothed" raptorial bill of the falcon for tearing meat, the small pointed bill of warblers for gleaning insects, the conical bill of sparrows and finches for cracking seeds, long needle-like bills of hummingbirds for reaching nectar in flowers, and even the Red Crossbill with offset mandibles designed to pry seeds from conifer cones.

Look in your bird identification guide and see if you can guess the feeding habits of a bird just by looking at the shape and size of the bill.


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