240 Wetmore, Birds of Lake Burford, N. Mex. [i£ril 



and was larger, thus resembling a male of the Black Duck group (possibly 

 A. diazi). No other ducks of this type were observed). 



9. Chaulelasmus streperus (Linnaeus). Gadwall. — The Gadwall 

 was the most common of the shallow water ducks at Lake Burford, out- 

 numbering the Mallards, as it was estimated that about 60 pairs were 

 breeding there. The birds were all in pairs at the time of my arrival but 

 appeared to nest late as males continued with the females until the time 

 of my departure. They shifted about more or less during the day but in 

 general were distributed all along the lake shore. On one occasion fifty 

 flushed in a flock from a shallow open bay and for a few seconds all were in 

 confusion. At once, however, the flock began to divide, and before they 

 had gone 150 yards all had separated out in pairs and flew off in that man- 

 ner. 



The mating flight of the Gadwall is always interesting and is seen con- 

 stantly when the birds are on their breeding grounds. Here at Lake Bur- 

 ford opportunities for observing it were excellent. The flight was usually 

 performed by two males and one female. In beginning two males approach- 

 ed a female in the water, calling and bowing. She usually rose at once 

 and flew with a slow flapping flight, mounting in the air with the males 

 in pursuit, calling and whistling constantly. First one and then the other 

 of the males swung in front of her, set his wings, inclined his body upward 

 to show his handsome markings, and, after a few seconds, dropped back 

 again to his former position. Late in the season there was always one of 

 the males who was favored and who displayed more often than the other, 

 flying close to the female, so that in passing his wings often struck hers, 

 making a rattling noise. After a short time the second male often left the 

 pair and returned to the water. The birds frequently mounted until they 

 were 300 yards or more in the air, and darted quickly from side to side, 

 flying now rapidly and now slowly. When the flight was over the birds 

 descended swiftly to the water again. I was never able to ascertain 

 whether there were some extra males about or not, as, though, there 

 were usually two with the female in this flight I found them at other times 

 always in pairs. 



The female Gadwall, like the mallards, also came out in the short grass 

 of the shore and walked about with head down, quacking loudly, an 

 action that I took for part of the mating display. 



When the birds were in the shelter of the rushes they went through 

 other mating actions of interest. The male swam toward the female bow- 

 ing by extending his neck until the head was erect and then retracting it, 

 bringing his bill down onto his breast. He then approached pressing his 

 breast against the sides of the female and shoving her easily, first on one 

 side and then on the other, biting her back and rump gently as he did so. 

 After a few seconds she lowered her body in the water and copulation took 

 place with the female entirely submerged save for the crown of her head 

 while half of the body of the male was under water. As the female emerged 

 the male turned immediately to face her and bowed deeply, giving a 

 deep reedy call as he did so. 



