WHERE WE STAND 



The migration of birds had its beginning in times so remote its 

 origins have been largely obscured and can be interpreted now only 

 in terms of present conditions. The causes underlying migration are 

 exceedingly complex. The mystery that formerly cloaked the 

 periodic travels of birds, however, has been largely dispelled through 

 the fairly complete information now available concerning the extent 

 and times of seasonal journeys of most species. Many gaps still 

 remain in our knowledge of the subject, but present knowledge is 

 being placed on record, and the answers to many uncertainties that 

 continue to make bird migration one of the most fascinating subjects 

 in the science of ornithology must be left for future studies. In some 

 areas we are on the threshold of discovery. More and more 

 sophisticated approaches including radar, radio telemetry, com- 

 puter processing of banding data, and physiological and behavior 

 studies are being developed. 



With the widespread use of these new techniques, we are beginning 

 to realize the benefits, aside from aesthetic reasons, for studying 

 migration. Radar alone has aided tremendously in documenting 

 flock size, heights, and speeds of migration as well as the descriptions 

 and locations of patterns and routes of specific migrants in relation to 

 aircraft flight lanes. Recent studies have indicated local, nonmigra- 

 tory populations of various blackbirds cause nearly all of the rice 

 damage in southern States and the "hordes from the North" 

 contribute very little to the losses. In addition, the transport of 

 arborviruses from one continent to another via these long distance 

 migrants is being investigated. People have started to uncover the 

 secrets of migration and utilize this knowledge for the betterment of 

 our society. 



Each kind of bird seems to have its own reaction to the 

 environment, so that the character of movement differs widely in the 

 various species, and seldom do any two present the same picture. In 

 fact, bird migration has been described as a phase of geographic 

 distribution wherein there is a more or less regular seasonal shifting 

 of the avian population caused by the same factors that determine the 

 ranges of the sedentary species. If this view is correct, then it must be 

 recognized that the far-reaching works of man in altering the natural 

 condition of the Earth's surface can so change the environment 

 necessary for the well-being of the birds as to bring about changes in 

 their yearly travels. The nature and extent of the changes wrought by 

 man on the North American Continent are readily apparent. 

 Extensive forests have been burned or cut away, rolling prairies 

 turned over with the plow, and wetlands drained or filled. Their 



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