132 NYROCA VALISINERIA 



Unfortunately the feeding grounds of these ducks are easily destroyed by heavy 

 ice which freezes down to the mud and sometimes results in the tearing away of all 

 the surface vegetation. Much more serious are the floods which have become com- 

 mon in recent years on the rivers of the Chesapeake and which, bringing down great 

 masses of silt, have from time to time destroyed some of the finest waters. The 

 German carp, which unluckily has found a new home in the shallower parts of some 

 of the Great Lakes and the fresher parts of the sounds of Virginia and the Carolinas, 

 destroys great quantities of vegetation. Fortunately our foreign population has no 

 objection to eating carp, and these coarse fish now find such a ready market in our 

 large cities that their numbers may perhaps be kept within reasonable limits. 



Courtship and Nesting. Evidently the full display of this species (see Plate 

 57) is only occasionally carried out. I have never seen it in the captive pairs which 

 I carefully watched throughout the whole spring. Apparently neither Wetmore 

 (1920) nor Harper (MS.) ever saw it in the field. Nevertheless, the birds do at times 

 go through the throw-back movement characteristic of the Pochard, Red-head, and 

 Golden-eye, for Mr. N. Hollister (in litt.) noted it on January 28, 1918, at the Na- 

 tional Zoological Park in Washington, and Mr. Wormald has seen it. The throw- 

 back is like the Red-head's but it is not indulged in so often and as nearly as I can 

 find out the head is never placed so far back over the tail. The note which is uttered 

 at the time, is almost exactly like the Red-head's. Wormald described it to me as 

 like a "wheezy Pochard." I often saw my own birds execute what I suppose might 

 be called a partial display, during the month of April. The males, sometimes several 

 at once, would suddenly stop swimming and run their necks up stiffly to a very erect 

 position, with their bills tilted upward well above the horizontal, while this position 

 was held from one to several seconds. A lump often appeared under the chin at this 

 time, caused apparently by inflation. Sometimes the bill was waved about in the air 

 as if the bird were trying to catch flies. The females at the same time executed similar 

 movements, but these were not carried out to so marked a degree. During all this 

 there was not a single sound uttered by either sex. Mr. Harper saw the same curious 

 neck-stretching in the field. In his manuscript notes he says: "On June 17 I noticed 

 a little courtship activity on the part of two males that were interested in a female. 

 One of the former had its neck stretched up, and threw up its bill a little. If it gave 

 any note at the same time, it was impossible for me to tell at a distance of two or 

 three hundred yards. Then the female took to wing, and the males followed, one of 

 them trying to fend off the other on the way. After alighting, the males seemed to 

 continue throwing up the bill, but not actively. In the meantime the female dove 

 for food, having probably come hungry from the nest. The whole affair was rather 

 tame." Evidently, then, the so-called pursuit flights do occur among diving ducks 

 as well as among surface-feeders. 



