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,
cephalopod{Taxobox| name = Cephalopods| fossil_range = | image = Tafel 054 300.jpg| image_caption = A variety of cephalopod forms from Ernst Haeckel's 1904 Kunstformen der Natur| regnum = Animalia| image_width = 220px| phylum = Mollusca| classis = Cephalopoda...
s, cetaceans, pufferfishes,
turtleTurtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
s, Anuran
tadpoleA tadpole, polliwog , or pollywiggle is the wholly aquatic larval stage in the life cycle of an amphibian, particularly of a frog or toad.- Appellation :The name "tadpole" is from Middle English taddepol, made up of the elements tadde, "toad", and...
s and sirens.
Anatomy
Beaks vary significantly in size and shape from species to species. The beak is composed of an upper jaw, called the
maxillaThe maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes , the maxilla is sometimes called "upper maxilla", with the mandible being the "lower maxilla"...
, and a lower jaw, called the
mandibleThe mandible or inferior maxillary bone forms the lower jaw and holds the lower teeth in place. It also refers to both the upper and lower sections of the beaks of birds; in this case the "lower mandible" corresponds to the mandible of humans while the "upper mandible" is functionally equivalent...
. 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
keratinKeratins are a family of fibrous structural proteins; tough and insoluble, they form the hard but un-mineralized structures found in reptiles, birds, amphibians, and mammals...
called the
rhamphotheca. Between the hard outer layer and the bone is a vascular layer containing
blood vesselThe blood vessels are the part of the circulatory system that transport blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart, the capillaries, which enable the actual exchange of water and chemicals between the blood and...
s and nerve endings. The rhamphotheca can include
knob, which is found above the beak of some swans, such as the
Mute SwanThe Mute Swan is a species of swan, and hence in turn a member of the duck, goose and swan family Anatidae. It is native to much of Europe and Asia, and the far north of Africa. It is also an introduced species in North America, Australasia and southern Africa...
, and some
domesticated Chinese geeseDomestic geese are domesticated Grey geese kept as poultry for their meat, eggs, and down feathers since ancient times.-Origins and characteristics:...
(
pictured).
The beak has two holes called
nares (nostrils) which connect to the hollow inner beak and thence to the respiratory system. 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
cereThe cere or operculum is a soft, fleshy swelling found on the beaks of certain birds. Hawks, parrots, doves, skuas and budgerigars are among the birds that have ceres. The word 'cere' is often used synonymously with 'beak', although the two are not identical...
(from
LatinLatin is an Italic language originally spoken in Latium and Ancient Rome. Through the Roman conquest, Latin spread throughout the Mediterranean and a large part of Europe...
cera, meaning wax). The cere is an indicator of the reproductive cycle of
budgerigarThe Budgerigar , is a small parrot and the only species in the Australian genus Melopsittacus...
s.
PetrelPetrels are tube-nosed seabirds in the bird order Procellariiformes. The common name does not indicate relationship beyond that point, as "petrels" occur in three of the four families within that group...
s and
albatrossAlbatrosses, of the biological family Diomedeidae, are large seabirds allied to the procellariids, storm-petrels and diving-petrels in the order Procellariiformes . They range widely in the Southern Ocean and the North Pacific...
es 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.. In the
mallardThe Mallard , probably the best-known and most recognizable of all ducks, is a dabbling duck which breeds throughout the temperate and sub-tropical areas of North America, Europe, Asia, Africa, New Zealand , and Australia...
, and perhaps in other
duckDuck is the common name for a number of species in the Anatidae family of birds. The ducks are divided between several subfamilies listed in full in the Anatidae article; they do not represent a monophyletic group but a form taxon, since swans and geese are not considered ducks...
s, 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
Beaks may be used to
pokePoke*An action of tapping and/or softly jabbing another person using a finger, stick, or similar object to gain their attention, relieve boredom or just to be annoying.Poke, Poké or POKE may refer to:...
, bite, grasp, maim,
stabSTAB or stab can have these meanings:*The act of stabbing with a sharp instrument*Stab, a short form of stab jacket, another word for buoyancy compensator*Stab vest, a type of armour designed to resist knife attacks...
, caw,
slashSlash may refer to:* Slash , the "/" punctuation character, also used in computing.* Slash fiction, a genre of fan fiction dealing with homosexual relationships or sexual encounters* Slash , woody debris generated by timber harvesting...
, pierce, tweet, call, ingest,
warnThe word warn may refer to:* WARN, a regional radio station* Worker Adjustment and Retraining Notification Act * Western Animal Rights Network...
and hook onto.
Billing
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 bondIn biology, a pair bond is the strong affinity that develops in some species between the males and or females in a pair, potentially leading to breeding. Pair-bonding is a term coined in the 1940s that is frequently used in sociobiology and evolutionary psychology circles...
(Terres, 1980).
GannetGannets are seabirds in the family Sulidae, closely related to the boobies.The gannets are large black and white birds, with long pointed wings and long bills. Northern gannets are the largest seabirds in the North Atlantic, with a wingspan of up to 2 metres...
s raise their bills high and repeatedly clatter them (
pictured); the male
puffinPuffins are any of three auk species in the bird genus Fratercula with a brightly coloured beak in the breeding season. These are pelagic seabirds that feed primarily by diving in the water. They breed in large colonies on coastal cliffs or offshore islands, nesting in crevices among rocks or in...
nibbles at the female's beak; the male
waxwingThe waxwings form the genus Bombycilla of passerine birds. According to most authorities, this is the only genus placed in the family Bombycillidae.-Description:Waxwings are characterised by soft silky plumage...
puts his bill in the female's mouth; and
ravenRaven is the common name given to several larger-bodied members of the genus Corvus—but in Europe and North America the Common Raven is normally implied.Species include:* Common Raven* Thick-billed Raven* Brown-necked Raven* Chihuahuan Raven...
s hold each other's beaks in a prolonged "kiss".
External links
- http://www.peteducation.com/article.cfm?cls=15&cat=1829&articleid=2752
- http://www.birdsnways.com/wisdom/ww53eiv.htm
- http://qp-society.com/qpserc/beak.html