Our little birds contributed to new scientific knowledge! I always let the children look through my Cabela’s polarized fishing spectacles, to identify polluted water or comprehend the effect of polarized light on sky, clouds, and vegetation color. (I once tried to get donations of the inexpensive glasses as Pollution Peepers, for the VISTAs/IGAPs to use as environmental prizes instead of candy and snacks.) Anyway, resetting the magnetic compass with polarized light is a clever solution, as the magnetic north wanders all over the place.
By Dennis O’Brien, Balto Sun reporter, Originally published August 11, 2006
…Biologists have known for decades that migrating birds use celestial cues and the earth’s magnetic field to find their way across continents and oceans.
But researchers from Virginia Tech in Blacksburg and Lund University in Sweden say experiments with savannah sparrows in Alaska show the birds take readings of polarized sunlight at sunrise and sunset and use them to periodically recalibrate their magnetic compasses….
Rays of ordinary light vibrate in different directions, but polarized light rays vibrate in only one direction – making them difficult for us to see. Birds that migrate at night use them at sunrise and sunset, when the rays are most evident, Muheim said.
In the study, Muheim caught 50 savannah sparrows in the Yukon Delta National Wildlife Refuge and threw off their celestial compasses by placing polarized light filters over their cages for an hour at either sunrise or sunset….
Read the article here
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