One of the most notable things about birds is their jaws and the fact that they have beaks properly called bills.
The bird's bill is a
remarkably adaptable and useful instrument. A good look at a bird pictures,
bird guide, or at birds in a zoo will show you some of the amazing diversity
in bird bills. Below are some drawings to illustrate the diversity of
the bills. When there are more complete images or descriptions of the
birds available they are linked to this information.
Different shaped bills serve different ecological purposes and are a good indication as to the bird's feeding habits. General purpose bills like the European Magpie or the Aristy have a general sort of diet involving a mixture of invertebrates and fruits. Some other examples are short thin bills for insect eaters, short thick bills for seed eaters, long thin bills can be for probing flowers for nectar or probing soft mud for worms and shellfish, strong hooked bills for tearing meat. The huge bills of Toucans and Hornbills are both decorative and functional. Being light, as well as long they allow the birds to pick fruit from the thin ends of branches that can not support the birds weight. Of course, food is not the only consideration and in birds the bill can play an important role in sexual selection, this is most notable in the Puffin whose bill grows a set of colourful scales during the spring to help in attracting a mate, in the spring? These scales are lost again making the bill duller and lighter as the season progresses.
Birds' bills are relatively lightweight structures as jaws go, weighing much less for their size than the comparable vertebrate jaws which involve bony supports and normally teeth.
A bird's bill is composed of a number of separate horny plates called rhamphotheca which are made of a protein called keratin (the same protein that makes our hair and a rhinoceros' horn). The rhamphotheca are fused together in most birds but some evidence can be seen of their individual existence in the bill of the Northern Fulmar, Fulmarus glacialis.
Some interesting Bird Bill facts
All birds have their nostrils at the basal end of the top mandible, except for the New Zealand Kiwi where they are at the tip.
The edges of the bill are especially hard and sharp and are called 'tomia', singular 'tomium'
The part where the two mandibles meet at the hinge of the bill is called the 'commissure'
No birds chew their food though they will use their bill to tear chunks off or to crush lumpy items before swallowing them.
Birds' bills continue to grow throughout the birds lives, this is necessary to replace the wearing that inevitably occurs at the tips.
When birds open their mouths it is the lower jaw that does most of the moving, most birds can move the upper jaw to some extent though only in a few groups like the parrots is it anywhere near as flexible as the lower jaw.
Puffins have an extra bone in their jaws which allows them to open their bill and to keep both mandibles parallel. This allows them to hold a whole row of fish without the ones near the tip falling out.
Flamingos use their bills as a sieve and plate just like a baleen whales to extract small algal filaments from the water.
The large bills of birds like Toucans are hollow and much lighter than they look.
Birds' bills are very sensitive, especially at the tips. Birds like Curlews can open the tips of their bills deep in the mud without getting a mouthful of mud.
The bills of some fish-eating birds have serrations along the edge to help them hold slippery fish. These are not real teeth.
The largest bill in the world belongs to the Australian Pelican, Pelecanus conspicillatus, 34-47 cm (13.4-18.5 inches)
Although a number of birds have upwards or downwards curving bill and a few like Crossbills have the tips curved to cross over each other, only the New Zealand Plover (Anorhynchus frontalis) has a bill curved to one side only (always to the right).
The Sword-billed Hummingbird (Ensifera ensifera) has a bill longer than the rest of its body.
Skimmers (Anhingidae) have their lower mandibles larger than the top ones. They fly with the lower mandible in the water and use it to flip fish up into the air where they can catch them.
The muscular response which snaps shut the bill of an Avocet, when it is sifting the soft mud at the edge of the tide for small shrimps, is one of the fastest ever recorded in the animal kingdom.
The bill of the Red-headed Woodpecker (Melanerpes erythrocephalus) hits the bark of a tree at about 21 km/h or 13 mph and the birds' brain experiences a deceleration of about 10G every time this happens.
The Black Woodpecker, Dryocopus martius, strikes with its bill against a tree between 8 and 12 thousand times a day.
Information on this page was contributed by EarthLife.
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