220 ANAS VALISINERIA. 



general whiteness of its plumage. A short comparison 

 of the two will elucidate this point : The canvass-back 

 measures two feet in length, by three feet in extent, 

 and when in the best order weighs three pounds and 

 upwards. The pochard, according to Latham and 

 Bewick, measures nineteen inches in length, and thirty 

 in extent, and weighs one pound twelve or thirteen 

 ounces. The latter writer says of the pochard, " the 

 plumage above and below is wholly covered with prettily 

 freckled slender dusky threads, disposed transversely in 

 close set, zigzag lines, on a pale ground, more or less 

 shaded off with ash ;*' a description much more applicable 

 to the bird figured beside it, the red head, and which 

 very probably is the species meant. In the figure of the 

 pochard given by Mr Bewick, who is generally correct, 

 the bill agrees very well with that of our red head ; but 

 is scarcely half the size and thickness of that of the 

 canvass-back ; and the figure in the Planches Enluminees 

 corresponds in that respect with Bewick's. In short, 

 either these writers are egregiously erroneous in their 

 figures and descriptions, or the present duck was 

 altogether unknown to them. Considering the latter 

 supposition the more probable of the two, I have 

 designated this as a new species, and shall proceed to 

 detail some particulars of its history. 



The canvass-back duck arrives in the United States 

 from the north about the middle of October, a few 

 descend to the Hudson and Delaware, but the great 

 body of these birds resort to the numerous rivers 

 belonging to and in the neighbourhood of the Chesapeake 

 Bay, particularly the Susquehannah, the Patapsco, 

 Potowmac, and James* rivers, which appear to be their 

 general winter rendezvous. Beyond this, to the south, 

 I can find no certain accounts of them. At the Susque- 

 hannah, they are called canvass-backs; on the Potowraac, 

 white-backs ; and on James' river, sheldrakes. They are 

 seldom found at a great distance up any of these rivers, 

 or even in the salt water bay; but in that particular 

 part of tide water where a certain grass-like plant 

 grows, on the roots of which they feed. This plant, 



