Life on the Edge: The Coming of Age of Quantum Biology by Jim Al-Khalili & Johnjoe McFadden

Author:Jim Al-Khalili & Johnjoe McFadden [Al-Khalili, Jim]
Language: eng
Format: epub
ISBN: 9781446488157
Publisher: Transworld
Published: 2014-11-05T21:00:00+00:00

In their 1972 experiments the Wiltschkos trapped the test birds in a shielded chamber and subjected them to an artificial magnetic field. Crucially, reversing the polarity of the field, by turning the magnet round by 180°, had no effect on their behaviour: the birds would orientate themselves in relation to the closest magnetic pole, whichever one it happened to be; so they didn’t possess a conventional magnetic compass. That 1972 paper established that the robins’ magnetoreceptor was indeed an inclination compass. But how it worked remained a mystery.

Then in 1974 Wolfgang and Roswitha were invited to Cornell University in the United States by the American bird migration expert Steve Emlen. In the 1960s he had developed with his father John, also a highly respected ornithologist, a special bird chamber that became known as an Emlen funnel.fn1 Shaped like an inverted cone, this funnel has an inkpad at the bottom and blotting paper on the interior sloping sides (figure 6.2). When a bird hops or flutters up the sloping walls it leaves telltale footprints that give information about the preferred direction in which it would fly if it could escape. The bird species the Wiltschkos studied at Cornell University was the indigo bunting, a small North American songbird that, like the European robin, migrates using some kind of internal compass. Their year-long study of this bird’s behaviour inside the Emlen funnel was published in 1976,12 and established beyond doubt that the indigo bunting, like the robin, was able to detect the geomagnetic field. Wolfgang Wiltschko regards the publication of this first Cornellbased paper as the team’s breakthrough moment, for it established beyond doubt that migratory birds have a built-in magnetic compass and caught the attention of many of the world’s leading ornithologists.

Figure 6.2: The Emlen funnel chamber.

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