Birds: The Inner Life

Granger Collection
John James Audubon: Red-Tailed Hawk, from Audubon’s Birds of America, 1827–1838

Like astronomy, ornithology is a science to which amateurs have made authentic contributions. Today, however, the divide between amateurs and professionals in ornithology appears to be deepening, as the professionals revolutionize our understanding of the ornithological family tree and of bird behavior by employing cellular biology and the chemistry of DNA.

Tim Birkhead, professor of behavioral ecology at the University of Sheffield, in Britain, has a remarkable capacity to bridge that gap. Author of highly respected technical work on the social and sexual behavior of animals, Birkhead is also capable of making his and others’ research clear, and even inviting. His skill lies in the way he poses his questions.

Birkhead worked that vein brilliantly in an earlier book, The Wisdom of Birds.
1 His subject was, more precisely, people’s wisdom about birds—a historical account of how humans have understood the actions and behavior of birds. But whereas most histories of ornithology have proceeded person by person, Birkhead worked concept by concept. Some concepts—migration, for example—are very old. Aristotle discussed it at length. Other concepts—such as territory—have come into focus only recently. Birkhead traced each concept back to its initial formulation, sometimes a very long time ago, and then followed successive refinements over time, some of them very recent.

The most effective pioneers, Birkhead found, were not always the famous names. Scientists missed some fundamental matters by relying too much on logic and prior authorities and not enough on observation, while hands-on bird keepers made decisive discoveries about such matters as territorial conflict, the seasonal character of birds’ sexual activity, and “migratory restlessness”—the agitation displayed by caged migratory birds when the lengthening (or shortening) day shows that it is time to travel.

Now Birkhead’s Bird Sense asks another intriguing question: How do birds perceive their universe? What does the world look like to a bird? He starts with Thomas Nagel’s 1974 article, “What Is It Like to Be a Bat?” But whereas Nagel concluded that we cannot know what it feels like to be another animal, Birkhead affirms that, while we can never share fully another creature’s experience, ingenious experiments now permit us to know a great deal about what birds can see, hear, smell, taste, and feel.

Sight and hearing are relatively simple matters. It has long been common knowledge that these senses are far more acute in birds than in humans. Only recently, however, has the full sophistication of avian sight and hearing been understood, along with their implications for the evolution of bird behavior. In the 1970s it was discovered that birds are capable of seeing the ultraviolet range of the spectrum, invisible to humans. Birds that look drab to us may be spectacular in ultraviolet light. Courting females choose males that are most brilliant in appearance (presumably an indicator of health and vigor), a process…

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