CANVAS-BACK 129 



clutches are far from exceptional. The Red-head is especially prone to mingle its 

 eggs with those of the present species. 



Voice. The male's voice is very rarely heard. Birds which I kept did not, during 

 the whole spring, make any sound that I could hear, but Mr. Ned Hollister writes me 

 that in the Washington Gardens he has heard males, during display, utter a "low, 

 wheezing call." Males observed by Wetmore (1920) at Lake Burford, New Mexico, 

 and those which Harper (MS.) studied on the Athabasca delta were entirely silent. 

 Even when actively courting the females, they uttered no sound that could be heard 

 at any considerable distance. But it is evident from Dr. Arthur A. Allen's (Bent, 

 1923) close study of confined birds that there is a perfectly definite courtship note 

 which he heard distinctly at twenty or thirty feet. This he describes as a tri-syllabic 

 ick, iclc, cooo with a little interval between the second and third sounds. When the 

 first two syllables are being produced the bird opens his bill slightly and then with 

 considerable force appears to inhale quickly, jerking his bill as he does so. "It 

 appears as though this sudden inhalation abruptly closes the glottis so as to produce 

 the two rather high-pitched, sharp, quick, ick ick notes." He then goes on to de- 

 scribe the swelling of the back of the neck and the accompanying low cooo sound. 

 He also saw the curious swelling which appears under the chin as the note is given. 

 Indeed, this lump under the chin is so prominent that I have seen it on birds a good 

 distance off. 



One occasionally hears the female call on the wintering grounds. Her note is a 

 coarse, guttural "churring" noise, usually represented by kurr-kurr-kurr, and 

 greatly resembling the call of the female Red-head and the Common Pochard. The 

 females are noisier in the spring and like other ducks will continually call when they 

 are accompanied by the young. At such times a note more nearly resembling a quack 

 has been heard by some observers. 



The trachea of the male is ten inches in length, gradually tapering toward the 

 lower end, but having a distinct enlargement one inch in length about three inches 

 from the upper end. The lower end terminates in a left-sided dilatation which con- 

 sists of an irregular flattened box, covered with membrane and very similar to the 

 same structure in the Red-head and the Pochard. 



Food. The favorite although not necessary autumn and winter food of the 

 Canvas-back is the so-called wild celery (Vallisneria spiralis) from which the species 

 has its name. This plant is so intimately associated with the duck that a short 

 description of it may not be out of place. McAtee (1911) describes it as a wholly 

 submerged plant with long flexible ribbon-like leaves of light translucent green color 

 and of practically the same width throughout the whole length. The leaves vary from 

 one-quarter to three-quarters of an inch in width. A leaf held up to the light displays 



