The variety of shapes and siz es of bird beaks reflect a marvellous evolution of nature even as they assist bir ds in carrying out different functions.
Words: BRINDA GILL
One of nature’s most endearing sights is of a bird flying with food in its beak for its chicks, and then carefully and gently placing that food in the opened mouths of the waiting brood. Never mind the size or shape of the beak, the parent bird carries out its task with utmost care that keeps the chicks well fed, growing and thus the species thriving. And in a marvel of nature, over millennia, bird beaks have evolved in different shapes and sizes from the tiny bill of a flowerpecker to the large beak with casque of the Great Hornbill, apart from colour and texture, to help birds source the food they eat, feed their young ones, and divide nature’s resources among the spectrum of avian species!
Like the Human Hand
While we initially think of a bird’s beak as its mouth, it actually is akin to a hand for the functions it carries out! For a beak, comprising an upper and lower mandible connected by bones and soft tissues, helps a bird source its food, carry it, eat it as well as feed its companion (the most endearing example being of hornbills) and its young ones.
Further, beaks also help birds in carrying out a variety of tasks from preening their feathers to releasing excess body heat in the summer (called panting), courtship rituals, building nests, defending themselves or fighting those who attack them with their bills.
Birds preen their feathers to keep them in good condition for health reasons and ease of flying. They do this by using their beaks to smoothen and align the feathers, as well as remove dust and any mites. Some birds have a preen gland at the base of the tail that produces an oily substance, and they use it to preen the feathers thus making them healthy, flexible and strong. While preening makes a bird healthy and attractive, interestingly it also forms part of courtship for some bird.
Beaks also help birds build their homes which range from the woodpecker incessantly banging its chisel-like beak into a tree trunk to make a cavity, the crow putting together twigs to build a nest in the crook of a tree branch, and the meticulous baya weaver bird making scores of trips carrying thin strips of grass or leaves in its beak and then using its beak to weave a lovely pendant nest hanging from a branch of a tree and the tailorbird using its beak to join the edges of a large leaf with stitches using plant fibre or spider’s web to make a nest.
Bills for Food Type
Some birds consume a variety of food, while most birds have very specific food preferences and their beaks have evolved to help them source and consume the particular food(s). So though some birds may look different, their beaks are of a similar shape as they eat the same food, and some birds appear similar to look at yet their beaks are of a different shape as they eat different food. A generalist like a crow will eat a variety of food from fruit to cooked rice and small birds/animals and its large stout beak helps it in doing just that. However, other birds are very specific about their food choices and their beaks are shaped just for that.
Thus, there are seed-eating birds like munias and sparrows with tough triangular-shaped beaks which give them power to break the outer casing of seeds; nectar-drinking birds like sunbirds who hover over flowers and draw the sweet liquid from deep inside a flower courtesy their long curved beaks that helps them probe flowers; fruit eating birds with small beaks like bulbuls; and fruit eating birds with larger longer beaks like parakeets. Insects, widely available, are eaten by a variety of birds including some that eat other foods. Insect eating birds have slightly longer, thinner beaks that
help them pick up insects and there are variations in beak type and size according to the surface or style of catching insects. And raptors that are meat eating birds like vultures, eagles, kites and owls use their feet to catch/kill their prey and then their hooked, sharp and strong beaks to tear the meat.
Birds that live near or in the water have another amazing variety of beaks. From the geese that feed on grass at the edge of the water and have broad, flat bills for straining water to get aquatic plants to kingfishers that have a pointed beak that helps them catch a fish and darters that have a long pointed beak to dart a fish. Pelicans stand out for their large beaks with a pouch below that helps them scoop up, hold and sieve a huge amount of water to obtain fish; its unusually sized beak has led to the observation “A marvellous bird is the pelican; its beak holds more than its belly can!”
Sharing Nature’s Resources
In this way, the different shapes of beaks ensure that the food available in nature is divided between different bird species. Further, nature also ensures that birds that feed on a particular food (such as seeds, fruits, insects or animals) get adequate food (thus dividing a particular food type between themselves) as beaks of the birds though of a similar shape are of different size. Similarly different nectar drinking bird species visit different flower types and have beaks of different shapes and sizes—some long and thin like the purple-rumped sunbird, and some long and with a pronounced curve like Loten’s sunbird as well as spiderhunters. Flowerpeckers also drink nectar, apart from berries, spiders and insects, and their beaks are shorter.
And though there are many species of meat eating birds, their beak sizes vary, so those with a relatively small beak (like shikra, harriers and buzzards) eat smaller creatures, while those with a larger beak like large eagles (Golden Eagle, S teppe Eagle and Eastern I mperial Eagle) will typically eat larger creatures. And as one observes the shape of beaks, it offers an insight into the type of food birds eat and possibly also the habitat they lives in, leaving one marvelling at the wondrous ways of nature!