Z4:0 Wetmore, Birds of Lake Burford, N. Mex. [April 



all day long and sometimes displayed for half an hour or more when no fe- 

 males were near. As a matter of fact this action often began whenever 

 I drove the males to open water from the shelter of the rushes, the 

 manner of procedure was as follows. The male rested on the water with 

 tail erect at an angle of 80 degrees. The head was then drawn in and 

 jerked rapidly up and down several times with the bill depressed, so that 

 the tip of the bill struck the side of the breast above the tracheal air sac 1 

 (present in the male alone) producing a curious clicking sound. The bill 

 tip was gradually lowered until at the last it hit the breast feathers at the 

 water line splashing the water into foam. At the same time the tail was 

 drawn steadily forward past the vertical to an angle of 60 degrees on the 

 opposite side of the arc, so that the tip came within one and one half or 

 two inches of the head. At the close of this action the head was suddenly 

 extended with the mouth open, and the bird emitted a low croak. The 

 tail was then thrown back to the usual position and the bird resumed its 

 normal attitude. In addition during the display the feathers of the crown 

 were elevated at the sides and depressed in the center to form a deep V 

 that was broad in front and more narrow behind. Sometimes birds held 

 the crest thus elevated constantly, and again it was thrown into this form 

 only as the last notes were given, when it was flattened immediately to the 

 normal position. The sounds produced during the display may be re- 

 presented by the syllables tick-tick-tick-lickety quek. The first series is not 

 vocal but is produced by the bill striking the breast above the swollen air- 

 sac, so that this sac is apparently used as a tympanum, a use which ex- 

 plains its development as a secondary sexual character in the male. The 

 last note is vocal and is made up of two distinct elements or sounds uttered 

 synchronously. One of these is a harsh frog-like note that may be repre- 

 sented by the syllable quok and the second is slightly drawn out, almost 

 two-syllabled, with a reedy quality resembling the note of the male Gad- 

 wall. It was thought that this second note was made in the normal way 

 by the syrinx, and that the first was caused by the expulsion of air from the 

 tracheal sac, as a contraction of the dermal muscle known as the cucullaris 

 above the sac was plainly evident through movement of the skin of the 

 neck as the duck extended his head and made this last sound. As this 

 note was given the tips of the wings were elevated for two inches or more, 

 so that it seemed possible that the carpal joint of the wings pressing against 

 the sac (which occupies the whole front of the neck above the breast) 

 aided in expelling air from it. 



Males were seen constantly swimming after the females, checking to 

 give the display, and then continuing on. At a distance they resembled 

 absurd little manikins with quick jerky motions controlled by the pulling 

 of strings. At short intervals the males extended their heads on the sur- 



x cf. Wetmore. A., Proc. U. S. Nat. Mus. Vol. 52, 1917, p. 479; and Condor. 

 Vol. XX, 1918, p. 19. 



