V ° L 192? VH ] Wetmore, Birds of Lake Burford, N. Mex. 229 



and so postpone the breeding season until a period of comparative 

 abundance had been reached. It would seem that this scant store 

 of energy must tell heavily on the females who were under the ne- 

 cessity of drawing upon their reserves of strength in producing a 

 number of eggs. The close of the breeding season finding the 

 birds thus reduced brings another call upon their vitality, in the 

 renewal of their covering of feathers. It was observed that fe- 

 male Mallards were renewing their body feathers at the same time 

 that they were mating and laying eggs. 



The occurrence of the Lesser Scaup Duck at Lake Burford was 

 of especial interest as, though the birds were present in fair num- 

 bers they were not breeding. These ducks were observed first 

 on May 25, when a few apparently were' mated. The mating dis- 

 play was observed on several days, and the birds were seen in copu- 

 lation occasionally during the first week in June. Two pairs that 

 were under observation frequented one area of rushes and the fe- 

 males gave the usual alarm note when I came in sight. Careful 

 search failed to reveal a nest and finally I shot both females, one 

 on June 17, and the second on June 18. Dissection showed that 

 while the ovaries in these two were apparently healthy, as they 

 were clear and normal in color, there was no physiological develop- 

 ment in ovary or oviduct, and careful examination showed that 

 the birds had not laid this year nor would they have done so if 

 unmolested. The reason that these ducks remain so far south is 

 puzzling. In many cases such ducks are cripples as I have taken 

 summering birds at such southern localities as Lake Koshkonong, 

 Wisconsin, Minco, Oklahoma, and the Laguna de Guanica, Porto 

 Rico, at the end of the month of May and during the first part of 

 June and have found that they showed the scars of old wounds. 

 Here at Lake Burford, however, the birds were present in fair num- 

 bers, and were able to fly without difficulty when approached, and 

 the two females collected showed no sign of injury of any kind. 

 The males observed were all in full handsome plumage. It may 

 be suggested that part at least of these ducks do not breed until 

 they are two years old, and that some of these may remain in south- 

 ern localities, lacking the physiological incentive for the flight to 

 the breeding ground in the north. 



An interesting case of sterility in a female duck was encountered 

 in collecting a small series of Mallards, to be preserved as speci- 



