272 BULLETIN 16 2, UNITED STATES NATIONAL MUSEUM 



During this procedure the whole musculature of the body seems to 

 be in a strained state of contraction, as if it required great effort on 

 the part of the bird. As the inflation of the orange-colored sacs 

 (it is really one large sac with two lateral areas devoid of feathers) 

 begins, the tooting sound is heard. Sometimes there is a slight 

 inflation before any sound is given. The inflation seems uniform 

 and does not fluctuate with the inflections and accents of the tooting 

 call. At the end of the tooting the sacs collapse suddenly by the 

 release of air through the nares or more rarely through the opened 

 mandibles. The sacs do not produce the notes, as was thought by 

 some of the earlier ornithologists, but have much to do with modi- 

 fying the sounds produced by the syrinx (the vocal mechanism at the 

 junction of the bronchial tubes). The sounds are produced by the 

 air forced from the lungs, which vibrates specialized membranes of 

 the syrinx under control of a complex set of muscles. The sound 

 waves then issue through the trachea and glottis to the pharynx. 

 In the production of such notes as the ordinary cackle the mandibles 

 are opened and the air accompanied by the sound waves issues out 

 of the mouth. In the tooting performance the mandibles are tightly 

 closed, the throat patch is elevated, and the tongue is forced against 

 the roof of the mouth (palate) by the mylohyoides muscles, which 

 close off the exit through the internal nares. The tongue is bent 

 in such a way that it causes the glottis at the base of the tongue 

 to open directly in front of the esophagus. The air now coming 

 from the respiratory system is forced to fill the modified anterior end 

 of the esophagus, or gullet, which becomes distended like a balloon. 1 

 While the air sac is filling, the sound waves produced by the syrinx 

 beat against these tense drumlike membranes, which serve as resona- 

 tors for the sounds and give them their great carrying power. The 

 ordinary cackles and screams of these birds seem louder than the 

 tooting or booming calls when one is near to the birds, but at a dis- 

 tance of 200 yards or more you can scarcely hear these calls, whereas 

 the booming carries for long distances, often 2 miles or more under 

 favorable conditions. 



The female's part in the courtship is a passive one. She minds 

 her own business, and I have never heard her utter any calls or notes 

 or show any concern in response to the ardent attentions of the males. 

 When a male or pair of males came strutting and circling about a 

 female she kept on with her feeding. If the males came too near she 

 merely stepped to one side and continued with the serious business 

 of procuring food. 



1 A number of detailed experiments were performed with both dead and living birds, 

 which clearly demonstrate the nature of the vocal mechanism as described above. See 

 Gross (1928). 



