Birds of a Feather
Find out how the body and beak shapes of birds give us clues about a bird's lifestyle, evolutionary inheritance and its approach to feeding. Exhibition currently closed..
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The north side of the lower balcony is home to birds, arranged in groups of close relatives. Their bodies give clues to their lifestyles, and each has a beak shape determined by its evolutionary inheritance and its approach to feeding.
The largest birds are unable to fly. This is seen today in the ostrich of Africa but is a more common feature on islands where birds are the top animals in the food chain. Apteryx australis is one of three species of kiwi in New Zealand, an island with no native mammals. Kiwis are small ground-dwelling birds with unusual feathers that are suited to insulation. The combined lack of a tail, large wings and strongly built feathers would make flight impossible. Kiwis are creatures of the night and have small eyes, relying more on their good sense of smell and long, sensitive bills to hunt out worms, small insects and fallen berries. Their eggs are large, up to one-sixth of the mother’s body weight. When nestlings hatch, they have to learn rapidly to fend for themselves.
Freshwater lakes and streams are havens for wild birds, and for a good reason: they are rich in food. The red-crested pochard Netta rufina is a member of the well-known duck family and has a typical duck bill shape. It also shares the common feeding habits of dabbling in shallow water and upending in search of water plants. This particular bird is from introduced stock, found in central Dublin but more at home in a belt stretching from southern Europe across Asia to China.
Many water birds are easily recognised by their bills, the shape of which is closely related to feeding habits. The typical dabbling shape of a duck’s bill contrasts with the long, probing bill of the curlew Numenius arquata. This is a common and widespread bird, familiar on mudflats and coastal grasslands anywhere from Ireland to Japan and as far south as Africa.
Even birds that are good fliers may spend much of their lives on the ground. The secretary bird Sagittarius serpentarius has long legs that are ideal for its hunting technique of stamping on snakes and other animals in short grassland. It has long wings, which are outstretched to defend its body against snakebites, and is a most graceful flier. The strongly hooked beak reveals its diet as a meat-eater. The feathers on its head resemble the quills that would have been used as pens by an 18th-Century secretary – hence its common name. The scientific name reveals its more vicious streak as the ‘archer of serpents’.
The most impressive predators among the birds are in the falcon family. They have evolved strong, curved bills for tearing meat, sharp claws for attacking prey, and very high speeds in flight. This group includes the more delicate falconets, such as Microhierax melanoleucus of India and South-East Asia, which feed on small prey but display the highly evolved flying skills of their larger relatives.
Some birds are less involved in the killing of animals, and prefer to spot their food from the air. The turkey vulture Cathartes aura is a widespread carrion feeder of North and South America. Like their giant relative, the condor, vultures have large nostrils and a keen sense of smell that can detect a dead animal from considerable distances. Their naked head region is useful in keeping this area clean, an advantage in a bird that feeds on entrails.