ORIENTATION AND NAVIGATION 



There probably is no single aspect of the entire subject of bird 

 migration that increases our admiration so much as the unerring 

 certainty with which birds cover thousands of miles of land and 

 water to come to rest in exactly the same spot where they spent the 

 previous summer or winter. Records from birds marked with 

 numbered bands offer abundant proof that the same individuals of 

 many species will return again and again to identical nesting or 

 winter feeding sites. 



This ability to travel with precision over seemingly featureless 

 stretches of land or water is not limited to birds but is likewise 

 possessed by certain mammals, reptiles, fishes, and insects; the well- 

 known migrations of salmon and eels are notable examples. 



For an animal to return to a specific spot after a lengthy migration, 

 it must use true navigation to get there. That is, it needs to not only 

 travel in a given compass heading and know where it is at any given 

 time so the course may be altered when necessary but also be able to 

 recognize its goal when it has arrived. It is dangerous to generalize on 

 the means of orientation and navigation in migration; different 

 groups of birds with different modes of existence have evolved 

 different means of finding their way from one place to another 

 (Pettingill 1970). We are only beginning to realize the complexities 

 involved in the many modes of bird orientation and navigation. All 

 we can do in this section is present a brief summary of some of the 

 more important principles involved and the studies that have 

 enhanced our knowledge in the area. 



Ability to follow a more or less definite course to a definite goal is 

 evidently part of an inherited faculty. Both the direction and the goal 

 must have been implanted in the bird's genetic code when the 

 particular population became established at its present location. The 

 theory is sometimes advanced that older and more experienced birds 

 lead the way and thereby show the route to their younger 

 companions. This explanation may be acceptable for some species 

 such as geese, swans, and cranes because they stay in family groups, 

 but not for species in which adults and young are known to migrate at 

 different times, especially when young migrate ahead of the adults. 

 As indicated in a previous section on segregation, many North 

 American shorebirds as well as the cuckoos of New Zealand do this. 

 An inherited response to its surroundings, with a definite sense of the 

 goal to be reached and the direction to be followed, must be attributed 

 to these latter birds. 



It is well known that birds possess wonderful vision. If they also 

 have retentive memories subsequent trips over the route may well be 



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