SUPPLEMENT TO BIRDS OF ESSEX COUNTY ' 51 



47 1^331 Anas rubripes rubripes Brewst. 

 Red-legged Black Duck; "Winter Black Duck." 



Abundant transient and winter visitor. September 22 to May i. 



When the original Memoir was published there was considerable doubt as 

 to the validity of this form then known as Anas obscura rubripes Brewst., and 

 my own observations, which, however, I admitted were insufficient, lead me to 

 think that it might be only the adult stage in the male of Anas obscura. Since 

 then I have made a further study of the subject and have convinced myself of the 

 validity of rubripes as a separate form, and I may add here that Mr. Brewster 

 considered my evidence conclusive. These studies were published in the Auk.^ 

 Since then, I have been able to show that the breeding Black Ducks of southern 

 Labrador belong to the tristis race. 



The Red-legged Black Duck is a virile race and the evidence seems to show 

 that it is increasing in numbers and extending its range farther south in winter. 

 Whereas it was formerly rare in winter at Currituck Sound, North Carolina, it 

 is now common. 



The numbers of this bird in the migrations and in winter vary. On Decem- 

 ber 17, 1914, I found a large number in the estuary between Hog Island and the 

 Ipswich dunes. It was a cold day ; the thermometer in the early morning stood 

 at 2° below zero Fahrenheit. There was no sun and no wind and snow was falling 

 intermittently. The tide was low, and in the shallow water amid the ice and on 

 the exposed flats were hundreds of Black Ducks. I counted 400 of these birds 

 and estimated that there were twice as many more or 1200 in all. Many were 

 sleeping, with their bills concealed in the feathers of their backs ; others were 

 swimming about, others feeding. A fleet of fifty came swimming rapidly around 

 a bar. In deeper water a flock of fifty or more Whistlers were diving for food. 

 When I discovered myself by springing up from the beach grass, the multitude 

 rose and made off with a great whirring and whistling of wings. ]\Ir. Charles W. 

 Loud writes me on September 6, 1918, that the bags of Black Ducks at Chebacco 

 Lake have been larger the past three years than for many years previous. 



Dr. Phillips^ says of the early flight of Black Ducks that he has record of 

 only three typical red-legged individuals ; while after October 20 they are com- 

 mon. The three early records for Red-legged Black Ducks were September 29, 

 1904, October 3, 1907, and October 9, 1906, all at Wenham Lake. 



iTownsend, C. W. Auk, vol. 29, p. 176-179, 1912. 

 1 Phillips, J. C. Auk, vol. 28, p. 191, 191 1. 



