Another specialized direct observation approach which has yielded 

 important information on the spatial and altitudinal distribution of 

 night migrating birds has been the use of small aircraft equipped 

 with auxiliary landing lights (Bellrose 1971). Major disadvantages of 

 night observation are that species cannot be identified and that birds 

 continue to migrate without a full moon. However, these techniques 

 do give information on the nocturnal migration movements that 

 could not be obtained by other methods. 



Aural 



An adjunct to the previously described nocturnal observation 

 methods, which has potential for species identification, is the use of a 

 parabolic reflector with attached microphone to amplify call (chip) 

 notes (Ball 1952; Graber and Cochrane 1959). This device, when 

 equipped with a tape recorder, can record night migrants up to 

 11,000 feet on nights with or without a full moon. A primary 

 disadvantage is that one cannot tell the direction a bird is traveling 

 and there is considerable difficulty in identifying the chip notes made 

 by night migrants. In addition, the bird may not call when it is 

 directly over the reflector and consequently it would not be recorded. 

 These calls are quite different from the notes we hear given by 

 familiar birds during the daytime while they are scolding an 

 intruder or advertising their territory. 



Preserved Specimens 



Reference material consisting of preserved bird skins with data on 

 time and place of collection exist in many natural history museums. 

 The essential ingredient in studying migration by this method is to 

 have an adequate series of specimens taken during the breeding 

 season so differences in appearance between geographically 

 separated breeding populations of the same species can be 

 determined. Such properly identified breeding specimens may be 

 used for comparison with individuals collected during migration to 

 associate them with their breeding areas (Aldrich 1952; Aldrich, 

 Duvall, and Geis 1958). This supplies a convenient way of recognizing 

 and referring to individuals representative of known populations 

 wherever they may be encountered. 



Marking 



If birds can be captured, marked, and released unharmed, a great 

 deal of information can be learned about their movements. Many 

 different marking methods have been developed to identify 

 particular individuals when they are observed or recaptured at a 

 later date. A few of the general methods are summarized in this 

 section. 



Bands, Collars, Streamers 



Since 1920, the marking of birds with numbered leg bands in 

 North America has been under the direction of the U.S. Fish and 



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