128 
CANVASS-BACK DUCK. 
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 poch- 
ard, 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 thick- 
ness 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 egregicusly 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 Susquehannah, 
they are called canvass-backs ; on the Potowmac, 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, which is said to be a species of Valisineria, grows on fresh 
water shoals of from seven to nine feet (but never where these 
are occasionally dry), in long narrow grass-like blades of four 
or five feet in length ; the root is white, and has some resem- 
blance to small celery. This grass is in many places so thick, 
