NOCTURNAL MIGRATION 67 



vantage of special training for racing, and even 

 where their previous flights have been limited to 

 short distances. A faculty of perceptive orientation, 

 in which the bird makes conscious or unconscious 

 note of the direction travelled, may however figure, 

 as in experiments by Hodge some years ago, pigeons 

 carried in an open cage to a point some distance 

 from their cote started for home without great de- 

 lay, while others whose cage during transit was cov- 

 ered closely by a black shawl seemed bewildered for 

 a time. 



The case of the migratory small bird is the more 

 complex since it performs much of its migratory 

 flight at night, indifferently in the light or dark of 

 the moon, at times under weather conditions when 

 landmarks cannot be visible for any considerable 

 distance. Also many of these flights carry the voy- 

 agers across broad stretches of open sea where there 

 are no lines of guidance of any description, if we 

 except certain steady winds that prevail in some 

 latitudes, or the possibility of following the lines of 

 ocean currents. 



Some have considered that birds that have pre- 

 viously made the southward journey serve as guides 

 for the young and inexperienced, which may be true 

 in a few cases but cannot be accepted as the full and 

 final explanation, since frequently old and young 

 birds migrate at different times. Adult cuckoos are 



