The skeleton will be examined, in the following order. Click below, to go directly to a section.
- Adaptations for Flight
- Pectoral Girdle
- Rib Cage
- Legs & Feet
Mallard ducks measure 58cm from the tip of the beak to the tip of the tail. The wingspan is 90cm. Their average weight is 1.1kg.
Adaptations for Flight
Birds have evolved to fly and have many unique features in their compact and lightweight skeleton. The skeleton makes up only about 5% of their total weight.
Many bird bones are hollow and filled with air sacs, linked to the lungs. These hollow bones are strengthened inside by a thin criss-cross structure, like honeycomb; the wing bones are like this.
Birds do not have heavy teeth and the associated jaw muscles; instead food is torn up by the beak, swallowed in larger pieces and broken down in the stomach, by the muscles in the gizzard. This adaptation moves the muscles and weight to the bird's centre of gravity, away from the head. In fact, the bulk of the bird's body is in the centre, underneath the wings. This makes the bird more stable in flight; it is unlikely to roll over, upside down, if its weight is all below it.
Many bones have been fused together to create rigid structures, which are light but strong. Birds have fused bones in the pelvis, chest, wings and legs.
The breastbone in birds is distinctive, with a large keel-shaped blade projecting forward to act as an anchor for the enormous flight muscles, which are not situated on the wings, but in the chest. It also helps provides stability in flight against conflicting air currents from the sides, as the keel stabilises a boat in rough water.
There is very little flexibility along the bird's body from the start of the shoulder blades to the tail. This prevents the bird's body being pulled and twisted out of shape, during flight.
Ducks have a long, broad skull with a wide, flat beak.
Bird skulls are generally made of light, delicate bone. You can see by the size of the eye sockets, that sight is their most important sense. The beak also dominates the skull. The brain case is small.
Bird skulls are strengthened by struts of bone, as you can see in the photo, below.
The large, oval hole at the base of the skull, the 'foramen magnum', is where the spinal cord goes into the brain case.
The eye sockets are high up on a duck's skull. This gives the duck, a prey animal, good all-round vision, so they can watch out for danger.
Ducks have small eyes, relative to the size of their skull, compared to a Tawny owl and House sparrow. The beak is proportionally much longer.
Beak / Bill
Birds have a tough layer of keratin around their upper and lower 'mandibles', or beak. Keratin is what nails, hair and feathers are made of. This sheath, called the 'rhampotheca', protects the tip of the beak, where it gets the most wear and tear, from feeding, preening and nest building.
Mallard ducks eat pondweed, seeds, acorns, berries, water plants, insects and larvae, small fish, slugs, snails and amphibians such as toads and frogs.
Ducks have a small bump on the tip of the upper side of their beak, called a 'nail'. It may be a different colour to the colour of the beak. The tough nail is used for hooking and moving items. The tip of the beak is very sensitive and covered in holes which connect to nerve endings. These help a duck feel for food in murky water and amongst the weeds.
The holes in the top of the beak are called the 'nares' or nostril. This is where air passes into the bird's lungs.
Ducks have rows of comb-like notches along the inside edge of the beak. These are called ‘lamellae’. They form a sieve, enabling a duck to sift out food items in the mud and water. Ducks fill up their mouths with water/ mud and then push their tongue upwards to force the mouthful out, through the sieve; the solid food items remain inside the mouth when the water is expelled. The lamellae also help a duck to grip its wet, slippery food.
Different species of duck have slightly different shape skulls and beaks. The lamellae vary too, in number, length and texture. Dabbling ducks, like Mallards, have 50-70 lamellae around the edge of both the upper and lower bills. Shoveler ducks have many more: 220 on the lower bill and 180 on the upper; the strands are longer and finer. Shovelers eat mainly invertebrates, in the water.
Birds do not have ears, or flaps of skin and cartilage like mammals do, which lead to the ear canal. They just have small ear holes which lead directly to the inner ear. The ear holes are below the eyes.
The spine is a line of tightly-interlinked bones, called 'vertebrae', which connect to form the central column in an animal's skeleton. The spine connects at the top, to the skull and extends to the tip of the tail.
In birds, the spine has little flexibility apart from in the neck and tail. This rigidity helps the bird's body resist the forces exerted by the wings in flight and keeps the body streamlined, reducing air resistance.
The spinal cord runs along a tunnel, called the 'neural canal', formed inside the vertebrae. Nerves branch out from the spinal cord, through gaps between the bones.
The shape of the vertebrae varies, depending on where they are: the different vertebrae are neck (cervical), chest (thoracic), lower back (lumbar), hip (pelvic) and tail (caudal).
The first vertebrae are the neck, or 'cervical' vertebrae. Different species of bird have different numbers of neck vertebrae.
Then come the chest, or 'thoracic', vertebrae, which connect to the ribs.
In birds,all of the lower back or' lumbar' vertebrae, the hip or 'sacral' vertebrae and some of the tail or 'caudal' vertebrae are fused with the bones of the pelvis to form the 'synsacrum'. This fusion of bones removes the flexibility which most animals have, in the middle of their spine.
A few tail, or 'caudal', vertebrae extend beyond the synsacrum.
The main photo shows the Mallard's tail vertebrae.
Birds cannot move their eyeballs within the sockets. They have evolved long, flexible necks, so they can twist their neck, instead.
Because birds have wings instead of arms or legs, they need to be able to reach around their body with the beak, for example to preen and manipulate food. A long neck helps with this.
Ducks have to twist their necks to squeeze preen oil out of the preen gland under their tail and spread the oil, using their beak, over their outer feathers, to keep them waterproof. Without this protection, a duck's feathers would quickly become waterlogged.
Different species of bird have different numbers of neck bones. Ducks have shorter necks than other water birds, such as geese and swans. They have 16 or fewer, neck vertebrae. Geese have 17-23 and swans have 24 or more.
The first group of vertebrae in the spine are the neck, or 'cervical' vertebrae.
The vertebra which connects to the skull is called the 'atlas'. This is a ring-shaped bone, which allows the head to nod.
The second vertebra is called the 'axis'. It has a ball shape on which the skull can swivel.
In mammals, the neck vertebrae are tightly stacked and have projections, called 'processes', which extend out to the side; these restrict the range of movement and strengthen the neck stronger.
By contrast, birds' neck bones are longer and more open, allowing more movement and the projections are much smaller; these two factors give the neck much greater flexibility. Look at the the photo below, to see how 'open' the birds' bones are and that they can easily swivel on one another.
In long-necked birds such as herons, geese, ducks and swans, one of the neck vertebrae is modified in shape and length to enable the long neck to bend comfortably into an S shape.
The pectoral girdle fits around the rib cage and anchors the bird's wings to the central core of the body.
The bones which form the 'pectoral girdle' are vital for flight. The girdle consists of four bones: two vertical, pillar-like 'coracoid' bones; two horizontal, elongated shoulder blades or 'scapulae'; fused collar bones, the 'furcula' and underneath, the large breastbone, or 'sternum'.
The two sturdy 'coracoid' bones are like pillars, connecting the sternum to the shoulder blades. This is an extra bone in birds, which braces the shoulder blades against the stresses of flight.
The long, narrow shoulder blade, or 'scapula', forms a large surface area on each side, for the shoulder muscles to attach onto. The shoulder blades lie back along the top of the ribcage, parallel with the spine. They glide over the surface of the ribcage, as the wings move up and down in flight.
The collar bones, or 'clavicles' are fused to form a U shaped bone, called the 'furcula' which rests in front of the rib cage. As a bird flies, the furcula acts like a spring, flexing in and out, as the wings move up and down.
The breastbone or 'sternum'. In birds which can fly, the breastbone is enlarged with a bony projection, shaped like the keel of a boat. The large muscles used for flying and swimming attach to this keel.
Each of the next five ribs attaches to the chest, or 'thoracic' vertebrae. These ribs have two sections: the 'vertebral rib' above, joined to the spine, and the 'sternal rib' below, connected to the sternum or breastbone. The final rib does not attach to the breastbone.
As you saw in the previous section, six of the tail or 'caudal' vertebrae are fused into the synsacrum. Six caudal vertebrae continue out from the synsacrum, as individual bones.
Finally, at the tip of the tail is a flat blade of bone called the 'pygostyle'. This is a fusion of the last four caudal vertebrae. The muscles which attach to it, help the bird to steer, take off and land, by adjustments of the tail.
Birds' wing bones follow a similar pattern to the human arm and hand. When not in flight, the wings fold up over the bird's body into three, in line with these three sections.
The first bone is a long upper arm bone, the 'humerus'. The major flight muscles on the breast attach to the humerus, which drives the wings.
There are two slimmer, forearm bones, the 'radius and ulna', which can slide over each other, as ours do. This enables a bird to twist its wing for steering, during flight. The mid wing, or 'secondary' flight feathers attach onto the ulna, the broader of the two bones.
Birds have two small wrist bones between the forearm and bones at the wing tip. The wrist and hand have fused into a blade-like bone called the 'carpometacarpus', which has an oval space in it. These bones carry the the main flight feathers, called the 'primaries'.
The thumb bones have become one small bone which projects out at the base of the 'carpometacarpus'. (Pointing to the right, in this picture.) This thumb bone supports the feathers of the 'alula', or 'false wing''; it is raised when a duck comes in to land, to prevent it stalling.
The bones of the second and third fingers have fused into one at the very tip of the wing, shown in the photo above. The bones of the fourth and fifth fingers have been lost completely, as bird skeletons have evolved.
Legs & Feet
Like most vertebrates, birds have a long thigh bone or 'femur', which connects to the pelvis or hip, with a ball and socket joint.
Below that the lower leg bone, the 'tibia' has fused with some of the foot bones to create the 'tibiotarsus'. The 'fibula' is like a thin pin, running alongside this bone.
The bones of the lower foot have fused to form another medium-length bone, the 'tarsometarsus', which appears to give a bird's leg, three sections.
The extended, third section of the leg helps birds take off and land. It also gives extra leverage when they jump forward, or paddle in the water.
In birds, the knee joint is usually covered in feathers and so is rarely seen. This makes it look as if a bird's knee bends backwards, but in fact the leg joint, which is visible below the body and feathers, is the ankle or heel.
Birds actually walk on their toes, not on their feet. This is described as being 'digitigrade'; they stand on their toes with their ankles in the air. They generally have four toes, three forward-facing and one, equivalent to our thumb, backward-facing.
The skin on the toes is scaly, offering protection against the wear and tear of walking, feeding and landing on branches.
The feet vary according to the habitat, lifestyle and diet of the bird. Ducks have webbing between their toes, so they displace more water when they paddle. They have claws to help grip on the mud and ice.
The Collector, Photographer & Author
I am Susanna Ramsey and I have a unique collection of natural history objects relating to British Wildlife. Over the last ten years, I have assembled an extensive range of skulls, skeletons, bones, skins, feathers, wings, antlers, insect specimens and taxidermy, all from animals in the UK.
During 2010-2018, I took my Nature Collection into local primary schools to display and run workshops for the children, linking the exhibition to science topics in the National Curriculum such as Adaptations, Bones, Classification, Food Webs, Habitats, Life Cycles and Local Wildlife.
In 2018-2020, I worked with the leading schools' catalogue, TTS ,to create a range of Educational Resources for primary schools, nurseries, after school clubs and families. To find out more about these products, click here or see below.
In the school workshops, children and teachers were always completely fascinated to see what is inside the animals we see everyday, in the garden or local parks. On these web pages, I want to continue to share my enthusiasm for the skeletons of our local wildlife. I hope you find these intricate structures as beautiful as I do.
BRITISH WILDLIFE PRODUCTS
If you know children who are interested in nature, are a teacher, or would like to learn more about British Wildlife yourself, explore the range of British Wildlife products recently created by The Nature Collection and the leading schools' catalogue, TTS.
The Classification: Natural History pack features 40 small photos of animal skeletons, skulls, feathers, insect specimens and much more, all from The Nature Collection!
The products are perfect for use in primary schools, nurseries, after school clubs, forest schools or at home with friends and family. Click on the links below to find out about each product.