Five Brilliant Bird Beaks
The earliest proto-birds, such as the famous Archaeopteryx, had heavy, tooth-filled jaws. But as birds continued to evolve and became increasingly aerial animals, they developed new ways of keeping their weight down. In addition to gaining hollow bones, their jaws changed too, into lightweight, versatile keratin structures – beaks.
Most bird beaks are not very effective at breaking up food (a special muscular compartment of the stomach – the gizzard – does most of this), so beaks have primarily become tools for simply collecting food. They have evolved in response to the food available in their habitats, resulting in a wide variety of beak shapes that reflect what and how they eat – from hooked weapons that can tear flesh from their prey to thin, delicate tools that probe for nectar. Below are just a few of the more unusual forms that beaks have taken in the bird world.
Wading birds are well-known for their beak variety. Sandpipers have small beaks, meaning they can only reach invertebrates a few centimetres below the surface of the sand or mud. Oystercatchers have a longer, straight bill, allowing them to probe deeper for cockles and mussels (though not usually oysters as their name suggests). And the curlew has a very long, downward-curving beak that can reach lugworms living quite far down in the sand.
The spoonbill, meanwhile, has a long, straight, flattened bill that broadens out at the end into a distinctive ‘spoon’ shape. There are six species worldwide (the royal spoonbill from Australia, New Zealand and parts of Southeast Asia is seen in the image at the top of this article), but they all feed in the same characteristic way; they sweep their partly-opened beaks from side to side through shallow water, increasing the chance that the large surface area of the bill will come into contact with prey. The moment any small aquatic creature touches the sensitive nerve endings on the inside of the bill, it snaps shut.
The Eurasian spoonbill is a rare breeding bird in the UK, though it is becoming increasingly common in the east and southwest of England. From a distance, it looks a bit like a large egret, though it has a habit of striding through the shallows with a strangely human-like walk, and it is unmistakable once that remarkable spatula-shaped bill becomes visible.
2. Openbill stork
When you have a specialised diet, you often need specialised tools to deal with it. The openbill stork is so named because its beak has an obvious gap between the two closed halves; they curve away from each other and only meet at the tip. This design is very useful for dealing with its preferred food, freshwater snails. It does not, as one might reasonably suppose, use its beak like a nutcracker for breaking the snails’ shells. Instead, it holds the snail in place using its upper mandible and then uses the tip of the lower mandible like a knife to slice through the muscle that holds the snail in its shell. Once that is done, the stork deftly extracts its meal, leaving the snail shell unbroken.
Pottering about among the shingles of New Zealand riverbanks is a small, inconspicuous plover called the wrybill. Its bill certainly does seem to have gone awry: it is the only bird in the world that has a beak that naturally bends to the side – and always to the right. By cocking its head to the left, the wrybill can slip this asymmetric instrument beneath a pebble, open its mandibles, and then scrape away any insect larvae, worms, or fish eggs that might be under there.
The crossbill is another bird whose name fits it perfectly. The mandibles of this finch’s beak, rather than meeting at a neat point at the tips, are instead crossed over. Like many birds with distinctive beaks, this is an adaptation to a specialised diet.
The crossbill feeds almost exclusively on the seeds of coniferous trees such as pine and larch. The problem with this is that these trees protect their seeds within a cone until they are fully developed. Only then does the cone open, scattering the seeds to the wind. These seeds are an important food resource for many small mammals and birds – but one that is not usually available until the cones open naturally. The strange beak of the crossbill, however, allows this bird to jump the queue. Using its crossed mandibles, it levers the tough conifer cones open and then scoops out the paper-thin seeds within using its muscular tongue. In doing so, this bird is able to exploit a rich source of food for many weeks before it becomes available to other, less specialised animals. Because their food supply is available year-round, crossbills can breed at pretty much any time; incubating females have even been seen in January, with snow on their backs.
There are five different species of crossbill in the world, and although all of them have crossed mandibles of some description, the particular size and shape of the bill vary between species, and even between populations within the same species. Each unique bill form is an evolutionary adaptation that enables the bird to specialise in prying apart the scales of their preferred type of cone, whether it be spruce, pine, or larch. Just as humans can be left- or right-handed, not all crossbills within a species have mandibles that cross the same way, although what determines the direction it takes is not yet understood. However, the proportion of left-billed to right-billed individuals is approximately equal, which implies that there are no disadvantages either way.
When a nestling crossbill hatches, its bill is straight, with the mandibles fitting neatly together. It isn’t until a few weeks later that its lower mandible begins to twist to one side or the other of the upper mandible; and another 10 days or so after that before it can start work on the cones upon which it will subsist for the rest of its life.
When a large bird resembling a hefty-looking blue-grey stork was discovered by scientists in the remote depths of Africa in the 19th century, several skins were sent back to Europe for examination. Its huge, thick, bulbous beak, in particular, was the subject of much discussion, prompting naturalists to call the bird the shoebill – they thought its bill bore more than a passing resemblance to a large shoe, especially a clog.
In 1851, the famous ornithologist and bird artist John Gould first laid eyes on this species. He described it as ‘the most extraordinary bird I have seen for many years’. It’s easy to understand why he thought that. Standing 1.5 m tall, and with a wingspan of 2.3 m, the shoebill is certainly a very striking bird. In fact, its size, coupled with that big, broad, capacious beak, a sinister ‘smile’ created by the fit of the mandibles, and an intense death stare make the shoebill somewhat of a formidable sight to behold. John Gould proceeded to give the shoebill the scientific name Balaeniceps rex, which means ‘king whale-head’.
Upon seeing the first dead specimens of the shoebill, some people assumed that the bird was an elaborate hoax, for they could see no reason as to why it would ever need such a massive, powerful beak. But of course, as always in nature, it does have a use.
Up to 20 cm in length, almost as wide, and with a viciously hooked tip, the outsized beak for which the shoebill is so renowned is perfectly adapted to catching large, slippery fish such as lungfish and eels in the muddy, stagnant pools of tropical Africa. Sometimes, the shoebill wades slowly through the vegetation-clogged water, ready to strike if it touches anything with its feet. But more often than not, this patient hunter stands completely motionless in a statuesque pose, sometimes for half an hour or more, waiting for fish in the poorly-oxygenated water to come to the surface for a gulp of air. Its distinctive, vivid eyes are more forward-facing than those of other wading birds, allowing it to accurately judge distance. When a fish finally appears, the shoebill suddenly lunges headfirst into the water, with the rest of its body following suit, creating a huge splash.
Once a fish has been caught and the shoebill has awkwardly righted itself, it dispatches its prey by cracking its skull or using the broad cutting edge of the beak to decapitate it. Then, the catch is swallowed whole. Sometimes, this bird uses its fearsome bill to catch and kill waterfowl, turtles, monitor lizards, and young crocodiles. There has even been a report of a shoebill killing and eating newborn swamp-dwelling antelope called lechwe.
Thanks to that huge, razor-sharp bill, its great size, and that fantastic scientific name, Balaeniceps rex (or B-rex, if you will), the shoebill has a very prehistoric aura about it. If anyone still doubts the link between dinosaurs and birds, I think they would need only to see a shoebill to be convinced. In my mind, few living species can remind us of the birds’ dinosaur ancestry than this unforgettable creature.
Choosing just five of the oddest beaks in the world proved too difficult, so I’ll be back in the future to reveal five more, including a species where the male and female have vastly different beak shapes, and a bird with a beak longer than the rest of its body.