STEGANOPODES. 



345 



frigate birds are perhaps unsurpassed in their command 

 of the wings in flight, although the albatrosses and the 



FIG. 116. Pelican (Galloway). Photographed by J. W. Folsom. 



petrels excel them in the ability to stay away from 

 land for a longer time. Frigate birds are frequently seen 

 hundreds of miles out to sea. This lightness of wing is 

 attained by the extraordinary system of air tubes under- 



