Bird Beaks or Bills Function & Anatomy
One of the most notable things about birds is their jaws and the fact that they have prominent beaks, properly called bills.
The bird’s bill is a remarkably adaptable and useful instrument.
A good look at a bird guide, or a zoo, will show you some of the amazing diversity in bird bills.
For those who do not have one of these available I have done some pretty awful drawings, to illustrate the diversity of these beaks. See what can you guess about the lives of these birds from the shape of their bills!
Different shaped bills serve different ecological purposes and are a good indication of 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 bird’s weight.
Of course, food is not the only consideration and the bird’s beak can play an important role in sexual selection. This is most notable in the Puffin whose bill grows a set of colorful scales during the spring to help in attracting a mate. After the spring these scales are lost again, making the bill duller and lighter.
Birds’ bills are relatively lightweight structures, as jaws go. They weigh much less for their size than the comparable vertebrate jaws – which involve bony supports and normal teeth.
A bird’s bill is composed of several 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 in most birds but some evidence can be seen of their existence in the bill of the Fulmar, Fulmaris glacialis.
Interesting Bird Beak Facts:
The top and bottom parts of a bird’s beak are called mandibles.
The upper bill or mandible is also called the maxilla.
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 bird’s 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 beak 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 whale to extract small algal filaments from the water.
The large bills of birds like Toucans are hollow and much lighter than they look.
Birds’ beaks are very sensitive, especially at the tips. Birds like Curlews can open the tips of their beaks 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, Pelicanus conspicillatus, 34-47 cm (13.4-18.5 inches)
Although several birds have upwards or downwards curved 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 vinifera) 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. 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.
Yes, most birds have tongues, though unlike ours a bird’s tongue has 5 bones in it that support and strengthen it. Together they are called the ‘Hyoid apparatus’.
There is also a great deal of variation in bird tongues.
A bird’s tongue is generally harder and less flexible than ours. Most birds have a relatively simple tongue, a flat triangular blade in shape with a few backwardly pointing papillae at the back of the mouth – which help to ensure food only goes in one direction.
In some birds, however, the tongue has become highly evolved.
In some fish-eating birds such as Penguins, the whole tongue is covered in backwardly pointing spikes which help in swallowing the fish. In other fish-eating birds such as Cormorants, the tongue has been almost completely reduced.
In Woodpeckers the tongue has become greatly elongated and is stored deep in the bird’s skull when not extended. Woodpeckers’ tongues also have a sharp pointed top to spear wood-boring insect larvae. The end of the tongue has backwardly directed barbs, to help in drawing the food items out of their holes in the wood.
Brush-tongued lories – as their name implies – have a tongue with a small brush at the tip. The brush is used to collect nectar from the various flowers that these birds visit. Other primarily nectar-feeding birds such as Hummingbirds, Sunbirds, and Honeyeaters have evolved tubular tongues.
These effectively give the bird a straw with which to suck up the nectar!
Finally, in parrots, the tongue has become thicker and more swollen – more like ours.
This helps parrots to manipulate their food in their mouths, but it also makes it possible for them to make all the sounds that endear them to us.