Smart Sea Birds, Clever Crows, and Birds With Bachelor Pads

Evidence indicates that other bird behaviors are culturally transmitted as well. For example, oystercatchers—black-and-white wading birds with long, red bills—use different strategies to dine on mussels. Observers have classified these birds into two groups, the “hammerers” and the “stabbers.” The hammerers have bills that are somewhat blunted on the end, while the stabbers have sharp bills. The beak assumes its shape over time as a result of the mussel-eating technique used by the bird.

Hammerers test mussels by tapping on the shells with their beaks, making a sound that reveals the thickness of the shell. If the sound suggests that the shell is thin, the bird breaks it open with hammering blows of its beak, a practice that flattens the end of the bill over the bird's lifetime. Stabbers, on the other hand, look for mussel shells that are already open. When a stabber finds an open shell, it quickly picks out the mussel from within before the shell can close.

Biologists believe that the method of getting into mussel shells favored by particular birds is determined by culture. They base this conclusion on observations of young oystercatchers learning one technique or the other from their parents.

Tool use by jackdaws, small crows that live on the South Pacific island of New Caledonia, is often cited as another example of a behavior that birds learn from one another. In 1996, biologist Gavin R. Hunt of Massey University in New Zealand reported more than 50 different instances of tool use within family groups of jackdaws. The birds made their tools from twigs, stripping the leaves and bark and tapering the ends to a sharp point. They also made hooked twigs that could be used as barbs. The birds held the twigs in their beaks and used them to capture insects from holes in trees and from under leaves. Gavin concluded that the jackdaws exceeded chimpanzees in tool-use skills.

Bowerbirds, which make up 18 species common to Australia and New Guinea, provide more evidence from the bird world of learning through imitation—and perhaps even of purposeful teaching by adults. Male bowerbirds construct elaborate structures, called bowers, to attract females. A bower consists of a large platform woven out of grass, twigs, and other vegetation with walls that form an arch over the structure. The males decorate these “bachelor pads” with various blue or green objects, including berries, shells, flowers, and buttons. Evidence for a cultural role in the building of the bowers comes from observations of young males that visit the bowers of older males early in the mating season. The young males spend a great deal of time observing as the older males tend the bowers and show off their plumage to the females. Groups of young males then work together to build “practice bowers,” taking turns arranging twigs, often clumsily and without success. Occasionally, older males assist the youngsters.