The Phenominal Speed of Bird Migration
By Dave Hanks
A big break-through in bird studies is the result of the invention of a tiny mechanism the size of a dime. The device is a light weight geolocator backpack that is attached at the base of a bird's spine. This is a location that doesn't off-set the bird's balance.
This device surprised researchers by revealing that migration speed is three times faster than was previously believed. One example: an individual leaving Brazil on April 12th will arrive on its USA breeding grounds by the end of the month. It is interesting to note that the desire to reach the breeding area results in a faster spring migration than the fall movement to warmer sites for wintering.
Most species migrate on a strict schedule - often the same day each year, which is determined by the length of daylight. To conserve energy, birds will ride thermal currents. Soaring is much easier than flap-flying. After the initial round trip, an individual can find their way - even if blown or thrown off course. It is almost as if one has a set of maps.
The GOLDEN-CROWNED SPARROW (pictured) breeds in southern Alaska and the Yukon, and winters in California. The relative short flying distance is a survival advantage for this species.
(At rest in a northern California shrub)
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