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Comparison of bird beaks, displaying different shapes adapted to different feeding methods. Not to scale.

The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, probing for food, courtship and feeding young. The term also refers to a similar mouthpart in some monotremes, cephalopods, cetaceans, pufferfishes, turtles, Anuran tadpoles and sirens.

Contents

Anatomy

Beaks vary significantly in size and shape from species to species. The beak is composed of an upper jaw, called the maxilla, and a lower jaw, called the mandible. The jaw is made of bone, typically hollow or porous to conserve weight for flying. The outside surface of the beak is covered by a thin horny sheath of keratin called the rhamphotheca. Between the hard outer layer and the bone is a vascular layer containing blood vessels and nerve endings. The rhamphotheca can include knob, which is found above the beak of some swans, such as the Mute Swan, and some domesticated Chinese geese (pictured).

The beak has two holes called nares (nostrils) which connect to the hollow inner beak and thence to the respiratory system.[1] The nares are usually directly above the beak. In some birds, they are in a fleshy, often waxy structure at the base of the beak called the cere (from Latin cera, meaning wax). The cere is an indicator of the reproductive cycle of budgerigars.[2]

Petrels and albatrosses have external horny sheaths called naricorns that protect the nares. These are separately placed on either side of the base of the upper mandible in albatrosses, but fused, with an internal septum, on the top of the base of the upper mandible in petrels.[3]. In the mallard, and perhaps in other ducks, there is no cere, and the nostrils are in the hard part of the beak, as a soft cere would be liable to injury when the duck dredges for food among submerged debris and stones.

On some birds, the tip of the beak is hard, dead tissue used for heavy-duty tasks such as cracking nuts or killing prey. On other birds, such as ducks, the tip of the bill is sensitive and contains nerves, for locating things by touch. The beak is worn down by use, so it grows continually throughout the bird's life.

Uses of beaks

As noted by Darwin in his observations on Galapagos Finches, birds' beaks have evolved to suit the ecological niche they fill: Raptors have decurved (downward curving) beaks for ripping up meat. Hummingbirds have long thin beaks for reaching nectar. The spoonbills' beaks allow them to filter-feed in shallow water. Unlike jaws with teeth, beaks are not used for chewing. Birds swallow their food whole, and it is broken up in the gizzard.

Billing

A fledgeling Common Starling shows the interior of its bill.

During courtship, mated pairs of a variety of bird species touch and clasp each other's bills. This is called billing and appears to strengthen the pair bond (Terres, 1980). Gannets raise their bills high and repeatedly clatter them (pictured); the male puffin nibbles at the female's beak; the male waxwing puts his bill in the female's mouth; and ravens hold each other's beaks in a prolonged "kiss".

Beak gallery

A variety of beaks
The bill of a scavenger—the Griffon Vulture.
The bill of a scavenger—the Griffon Vulture
The bill of a domesticated Chinese goose. The knob is highly exaggerated by farm selection.
The bill of a domesticated Chinese goose. The knob is highly exaggerated by farm selection. 
Northern Gannets billing.
Northern Gannets billing. 
The bill of the Greater Flamingo.
The bill of the Greater Flamingo
The beak of a Brown Falcon.
The beak of a Brown Falcon
The beak of an African Penguin.
The beak of an African Penguin
The long white beak of a Long-billed Corella is used to dig for roots and seeds.
The long white beak of a Long-billed Corella is used to dig for roots and seeds. 
The beak of a Catalina Macaw
The beak of a Catalina Macaw 
The beak of a malabar grey hornbill
The beak of a malabar grey hornbill 
A golden eagle's beak
The beak of a golden eagle 

See also

References

  • Gilbertson, Lance; Zoology Lab Manual; McGraw Hill Companies, New York; ISBN 0-07-237716-X (fourth edition, 1999)
  • Terres, John. K. The Audubon Society Encyclopedia of North American Birds, New York: Alfred A. Knopf, 1980. ISBN 0-394-46651-9

1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

BEAK (early forms beke and becke, from Fr. bec, late Lat. beccus, supposed to be a Gaulish word; the Celtic bec and beq, however, are taken from the English), the horny bill of a bird, and so used of the horny ends of the mandibles of the octopus, the duck-billed platypus and other animals; hence the rostrum (q.v.) or ornamented prow of ancient war vessels. The term is also applied, in classic architecture, to the pendent fillet on the edge of the corona of a cornice, which serves as a drip, and prevents the rain from flowing inwards.

The slang use of "beak" for a magistrate or justice of the peace has not been satisfactorily explained. The earlier meaning, which lasted down to the beginning of the 19th century, was "watchman" or "constable." According to Slang and its Analogues (J. S. Farmer and W. E. Henley, 1890), the first example of its later use is in the name of "the Blind Beak," which was given to Henry Fielding's half-brother, Sir John Fielding (about 1750). Thomas Harman, in his book on vagrants, Caveat or Warening for commen cursitors, Vulgarely called Vagabones, 1573, explains harmans beck as "counstable," harman being the word for the stocks. Attempts have been made to connect "beak" in this connexion with the Old English beag, a gold torque or collar, worn as a symbol of authority, but this could only be plausible on the assumption that "magistrate" was the earlier significance of the word.


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Simple English

with a orange-red beak.]]

A beak is the nose and mouth of a bird or octopus. It is used for eating, fighting and many other things. An example of this is the duck. Some kinds of insects have mouths that are very long and narrow and is called a beak.








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