Orientation in Birds

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Peter J. Hore of Oxford University, are now available in a paper entitled "Anthropogenic electromagnetic noise disrupts magnetic compass orientation in a migratory bird," published in the latest issue of the journal Nature. Nature underlines the importance of this study by making it the cover story of its May 15th issue.


This interference does not stem from power lines or mobile phone networks," Mouritsen stresses, explaining that electromagnetic interference within the two kilohertz to five megahertz frequency range is mainly generated by electronic devices. It all started with a stroke of luck. For around 50 years it has been known that migratory birds use Earth's magnetic field to determine their migratory direction. Biologists have proven this in numerous experiments in which they tested the birds' navigation abilities in so-called orientation cages.

Nils-Lasse Schneider, an electrophysiologist and researcher in Mouritsen's work group, then came up with the idea that set things in motion: he proposed covering the wooden huts, along with the orientation cages they contained, with sheets of aluminium.

migration of animals: Orientation and Navigation

This did not affect Earth's magnetic field, which is vital for the birds to navigate, but it strongly attenuated the time-dependent electromagnetic interference -- the electrosmog -- inside the huts. The effect was astounding: suddenly the birds' orientation problems disappeared. The surprising thing here, the biologist adds, was that the intensity of the interference was far below the limits defined by the International Commission on Non-Ionizing Radiation Protection and the WHO.

Considering the potential importance of the finding, Mouritsen and his team performed a large number of experiments to provide evidence of the effect they observed: "Over the course of seven years we carried out numerous experiments and collected reliable evidence, in order to be absolutely certain that the effect actually exists. Several generations of students repeated the experiments independently of one another on the Oldenburg campus. What they found was that as soon the grounding of the screens was disconnected or electromagnetic broadband interference was deliberately created inside the aluminium-clad and earthed wooden huts, the birds' magnetic orientation ability was immediately lost again.

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Furthermore, the scientists were able to show that the disruptive effects were generated by electromagnetic fields that cover a much broader frequency range at a much lower intensity than previous studies had suggested. This electromagnetic broadband interference is omnipresent in urban environments.

It is created wherever people use electronic devices. As expected, it is significantly weaker in rural areas. And indeed, unlike on the University campus, the magnetic compass of the robin did function in orientation cages placed one to two kilometres outside city limits, even without any screening. However these findings should make us think -- both about the survival of migratory birds as well as about the potential effects for human beings, which have yet to be investigated," Mouritsen concludes.

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Materials provided by University of Oldenburg. Note: Content may be edited for style and length.

migration of animals: Orientation and Navigation | Infoplease

The Development of Migratory Orientation Mechanisms. Evolutionary Aspects of Orientation and Migration in Birds. Ecological Causes and Consequences of Bird Orientation. Orientation in birds: A final consideration.

Back Matter Pages About this book Introduction If it is true that science proceeds from a romantic through a scientific to a technological stage, then research on bird orientation is certainly on its move from its first to its second grade, and recent developments in radiotelemetry and satellite tracking of migrating birds might already indicate the advent of the third stage. At this juncture, Orientation in Birds is a timely account. Even though the study of animal migration in general, and bird navigation in particular, has produced a literature of impressive proportions, the threads provided by the plethora of research papers, review articles and symposiums volumes have not yet been knitted into a theoretical fabric.

The answer to the most intriguing question of how a bird displaced to "unknown" territory finds its way back home is as obscure now as it was a few decades ago. Whether and how birds solve this problem by using far ranging grid-maps or more local familiar-area maps, as has been proposed off and on, is still a matter of heated debates. These debates frequently center around provocative hypotheses - let alone the question about the physical topographic, magnetic, infrasonic, olfactory parameters which might constitute such maps.

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