Bird beaks

A beak for every purpose

Article and images by Dr Julie O'Connor, senior conservation partnerships officer

There are around 10,000 bird species on the planet. They all share certain physical characteristics, including feathers, wings (although not all birds fly) and beaks. All birds, from the tiniest bee hummingbird (Mellisuga helenae) weighing less than 2g to the huge ostrich (Strutheo camelus) weighing in at a hefty 150 kg, have evolved beaks adapted to their diet. This allows them to exploit their own prey niche.

Spatula shaped beaks of the dabbling ducks, such as the Pacific black duck and the introduced mallard duck, assist them to eat plants and small invertebrates. The filter feeding process is helped by small pointed projections called lamellae. In the absence of teeth, these act like strainers to keep in plants and bugs but allowing water and mud to flow back out.

The 6 species of flamingos are also filter feeders, but their beak design is different. Unlike other birds, the bent beak of the flamingo allows the flamingo to feed upside down in the water. Flamingos have 2 rows of lamellae in both the upper and lower mandibles. These mesh together when the beak is closed to allow water to flow out while keeping in shrimp, algae, diatoms and other food items. The large lower mandible of the Chilean flamingo allows it to eat larger food items such as shrimp and molluscs.

All the raptors have powerful hooked beaks that share some commonality in design. Their differences reveal their dietary purpose. For example, the Australian boobook (Ninox boobook) eats birds up to the size of a house sparrow and small mammals, particularly the house mouse (Mus musculus). It also eats more invertebrates than other Australian owls. Australia’s largest raptor, the wedge-tailed eagle (Aquila audax) has a very strong beak capable of ripping apart rabbits, hares, wallabies, koalas, wombats and sometimes introduced foxes and cats.

The tawny frogmouth (Podargus strigoides) is well known for its large gaping mouth. The large gape helps it to scoop prey from the ground, an action further assisted by the modified feathers around the mouth which help to guide the prey into the mouth.

The swifts and swallows also have their own prey niches and the beaks necessary to do the job. Like many other insect catchers and the tawny frogmouth, they have modified hair like feathers around their beak to help guide their prey into their mouth.

There is also much diversity among the parrots of the world, although they generally have large beaks with mobile tongues to help them manipulate food. Seed predators like the macaws have beaks powerful enough to break open tough tree nuts like Brazil nuts. Rainbow lorikeets have strong beaks but are also equipped with a brush-tipped tongue to help them drink nectar and eat soft fruits.

Most hummingbirds have long beaks with long tongues that enable them to sip nectar from flowers. There are around 300 hummingbird species, each with its specially adapted beaks to extract nectar from its flowers of choice. While most have long beaks and tongues to allow them to access deep into the flower, a small number of hummingbirds have short beaks. They use this to stab the base of the flower to extract the nectar.

Kingfishers have long dagger-like beaks, although the beak of our most famous kingfisher, the laughing kookaburra (Dacelo novaeguineae) is not as long and streamlined as its river and water cousins. The beak shape of the diving kingfishers is so efficient that it served as inspiration for a redesign of Japan’s famous bullet train. Designers were finding that the bullet train boomed when entering a tunnel. This was due to the pocket of air that the speeding train built up in front of it. One of the engineers working on the problem was a keen birdwatcher and had noticed how little splash a kingfisher made on entering the water. When engineers applied a modified version of a kingfisher beak to the shape of the nose of the train, the booming problem was solved.

The darters have spectacular beaks that advertise their preferred method of hunting. The Australasian darter uses its long beak and snake-like neck to spear fish under the water. Sometimes the catch is eaten underwater but larger fish are brought to the surface, flicked from the beak, then caught and swallowed whole.

Next time you are out watching any of these little feathered marvels, have a think about which dietary adaptation might have shaped the beak of the bird you are watching.

References

• Howe RO. A comparison of hydrodynamic performance in bills from kingfishers (Alcedinidae) with differing feeding strategies, with implications into the foraging behaviour of the most recent common ancestor, Prifysgol Bangor University.
• Moore, David E, 2019, Zoology: Understanding the animal world, lecture series, The Great Courses.