nonhunted species that winters in South America. Over 500,000 

 chimney swifts have been banded, but only 21 have been recovered 

 outside the United States (13 from Peru, 1 from Haiti, and the rest 

 from Mexico). The conclusion is simply this: Whereas banding is very 

 useful for securing certain information, the volume of birds that need 

 to be banded to obtain a meaningful number of recoveries for 

 determining migratory pathways or unknown breeding or wintering 

 areas may be prohibitive. One problem in interpretation of all 

 banding results is the fact that recoveries often reflect the 

 distribution of people rather than migration pathways of the birds. 

 Other methods used to mark individuals in migration studies 

 include clipping the tip end off a feather (not a major flight feather) 

 with a fingernail clipper or touching the feather with colored paint or 

 dye. This marking technique is obviously good for only as long as the 

 bird retains the feather (usually less than one year), but allows the 

 investigator to recognize whether the bird has been handled 

 previously or not. 



Radio Tracking 



One of the most promising methods of tracking the movements of 

 individual birds in migration has been developed in recent years. It is 

 called radio tracking, or telemetry, and consists of attaching to a 

 migrating bird a small radio transmitter that gives off periodic 

 signals or "beeps". With a radio receiving set mounted on a truck or 

 airplane, it is possible to follow these radio signals and trace the 

 progress of the migrating bird. One of the most dramatic examples of 

 this technique was reported by Graber in 1965. He captured a 

 grey-cheeked thrush on the University of Illinois campus and 

 attached a 2.5-gram transmitter to it (a penny weighs 3 grams). The 

 bird was followed successfully for over 8 hours on a course straight 

 across Chicago and up Lake Michigan on a continuous flight of nearly 

 400 miles at an average speed of 50 mph (there was a 27 mph tail 

 wind aiding the bird). It is interesting to note that while the little 

 thrush flew up the middle of Lake Michigan, the pursuing aircraft 

 skirted the edge of the lake and terminated tracking at the northern 

 end after running low on fuel while the bird flew on. The limitations 

 of radio telemetry, of course, are the size of the transmitter that can 

 be placed on birds without interfering with flight and the ability of 

 the receiving vehicle to keep close enough to the flying bird to detect 

 the signals. Despite this difficulty there has been considerable 

 development in the technology, and encouraging results to date give 

 promise for the future, particularly when receivers can be mounted 

 on orbiting satellites (Graber 1965; Bray and Corner 1972; Southern 

 1965). 



Radar Observation 



One of the developments of our modern age of electronics has been 

 the discovery that migrating birds show up on radar screens used in 

 monitoring aircraft. At first, the screen images caused by flying 



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