The varied anatomy of the feet of birds is one of the many fascinating aspects of the avian world.
Without any qualms a small purple sunbird settles on a flower high up a lofty silk cotton tree drinking its sweet nectar while holding itself securely on the bobbing blossom with its delicate feet. Descending from the air, with a smooth swoop, a black kite picks up a prey with its feet, grasps it firmly with its talons, and flies to a safe spot to eat it with its beak while the prey is held in the talons. On a forest floor, birds of the pheasant and fowl families are seen scratching the earth with their feet to forage insects and seeds. Near a water body surfaced with lilies are sighted jacanas walking from land onto the large circular leaves with equal ease while almost giving it an appearance of walking on water. And in the waters, a bevy of ducks is invariably spotted rhythmically moving their webbed feet to paddle around effortlessly. All these glimpses of birds convey the fantastic role played by their feet in carrying out different tasks.
Varied Feet Structures
Even casual observation shows different bird species have feet of different structure and strength. The varied anatomy of birds’ feet do indicate that the fascinating hand of evolution that has resulted in bird feet developing in response to the habitats they live in, the food they source and their style of consuming it. For instance, the independent four toes of crows help them perch on trees; the toes of birds that stalk the waters (like herons) are slim and long helping distribute the bird’s weight as it walks on water soaked ground and shallow waters; the toes of cranes that walk in fields as well as water are long and strong; the toes of ducks are connected by webbing that helps them paddle in water.
Most birds have four toes, with few species having a different number of toes such as emus and bustards have three and ostriches two. In some birds – like fowl and pheasants – the fifth toe appears as spur used for defence. In some cases, birds may have two toes fused such as kingfishers (third and fourth are partially fused), and this helps them excavate burrows in earthen banks for nesting.
Further, the toes may be short or long, thick or thin, independent or webbed, and occasionally have other features such as fleshy lobes. And talons (curved and pointed appendages on toes commonly called nails) that help birds in catching, crushing and carrying prey. Osprey, that is a fish eating bird, has some special adaptations: its talons are pronouncedly curved to help the bird hold on to the fish once it is caught, and the sole of its feet is very rough to help it grip fish in water.
Of Toes and Webs
Perching birds have four independent, flexible toes. Of these, birds like crows and sparrows have three toes pointing forwards and one pointing backwards that help them hold branches securely and balance.
Yet there are perching birds like woodpeckers that have two toes facing forwards and two facing backwards that help them balance and grasp the trunk of trees as they climb up and around. Further, some species of birds have toes that can be rotated when required. And swifts, that spend most of their time in the air, are noted for their ability to turn all four toes of their tiny feet pointing forwards or rotate the outer two backwards to help them hold onto surfaces vertically or even upside-down.
Many birds that live near water have feet adapted to walk on wet, sandy or marshy areas as well as water in the form of feet that have long toes or are webbed. Yet, there are interesting variations even within these feet types. There are some birds (ducks) that have three front facing toes that are fully connected with webbing and one independent back facing toe; then birds (some herons) that have three front facing toes that are partially connected with webbing and one independent back facing toe; birds with four forward facing spread out toes that are all connected by webbing (such as pelicans); and birds (such as coots) with three front facing toes with lobes (and one back facing toe without lobe) that helps them kick in water, and walk on land when the lobes fold back.
Of Flightless Birds
The feet of flightless birds have fascinating details as well. Ostrich – a terrestrial flightless and the largest of any living bird – has only two toes on each foot, the larger one to bear the weight of the bird and the smaller one for balance. Penguins, aquatic flightless birds, have webbed feet that enable them to walk, propel and steer themselves on icy stretches and jump, as well as paddle in water, and they also incubate their eggs by placing them on their feet.
The bare feet of penguins do not freeze even when they stand on icy surfaces due to a counter-current heat exchange mechanism. While these details are fascinating for nature lovers, scientists and researchers study them to know how feet have adapted to habitat and ecology, and reflect the habitat a bird lives in.