STEGANOPODES. 



345 



frigate birds are perhaps unsurpassed in their command 

 of the wings in flight, although the albatrosses and the 



Fig. ii6. — 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- 



