A model photochemical compass for bird ...( A team of researchers at Arizona Sta...)

A team of researchers at Arizona State University and the University of Oxford are the first to model a photochemical compass that may simulate how migrating birds use light and Earth's weak magnetic field to navigate. The team reports in the April 30, 2008, online issue of Nature that the photochemical model becomes sensitive to the magnitude and direction of weak magnetic fields similar to Earth's when exposed to light. The research funded by the National Science Foundation (NSF) demonstrates that this phenomenon, known as chemical magnetoreception, is feasible and gives insight into the structural and dynamic design features of a photochemical compass.

The most common bird migration pattern in the northern hemisphere is to fly north in the summer to breed in the Artic and to fly south to warmer regions for the winter.

Regardless of which way they are flying, migrating birds are important ecologically as a food source for other animals. They also transport plankton, materials involved in plant reproduction and hitchhikers such as ticks and lice, which can carry micro-organisms harmful to human health.

About 50 animal species, ranging from birds and mammals to reptiles and insects, use Earth's weak magnetic field for navigation. Earth's magnetic field ranges from approximately 30 to 60 millionths of one tesla. By comparison, magnetic resonance imaging, or MRI, uses magnetic fields from 1.5 to 3.0 tesla.

Weak magnetic fields are also produced by widely used technologies such as power lines and communications equipment. Because these man-made magnetic fields can disrupt animal navigation, "it is essential for humans to understand how animals navigate using Earth's weak magnetic field and the effects of human activity on animal navigation," according to Devens Gust, foundation professor of chemistry and biochemistry at Arizona State University.

Even though the mechanisms of a bird's internal compass have been s
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