NOCTURNAL MIGRATION 49 



did not perceive them. Aviators have recorded such 

 birds at 10,000 and 12,000 feet. Pelicans, cranes, 

 ducks, and geese often pass at 3,000 to 8,000 feet in 

 travelling from one feeding ground to another, and 

 when crossing mountain chains mayfly at enormous 

 heights. Donald notes that in the Himalayas, at 

 14,000 feet above sea-level, he observed storks and 

 cranes flying to the northeast at the end of May, 

 when they were so high that they could be seen only 

 through glasses. Meinertzhagen considers that, if 

 these birds were beyond unaided vision, they must 

 have been at least 6,000 feet above the earth, placing 

 them at an actual altitude of 20,000 feet above the 

 mean level of the sea. 



Captain C. Ingram ^ has assembled other observa- 

 tions by aviators, and has obtained results fully in 

 agreement with those given above. It is of interest 

 to examine the greatest altitudinal records that he 

 gives. Lapwings and ducks were noted up to 8,500 

 feet, though rarely seen above 6,000 feet. Geese 

 were seen at 9,000 feet, and sandpipers of unknown 

 species at 10,000 and 12,000 feet, above the battle- 

 front in France. Small birds with undulating flight 

 were recorded once at 10,000 feet. These, however, 

 were such unusual occurrences that the aviators 

 making the records took special note of them. Dr. 

 A. F. R. Wollaston, when on the Mount Everest 



I Ibis, 1 91 9, pp. 321-325. 



