CANVASS-BACK DUCK. 
109 
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 Hud- 
son and Delaware, but the great body of these birds resort to the 
numerous rivers belonging to, and in the neighborhood of, the 
Chesapeake bay, particularly the Susqiiehannali, the Patapsco, 
Potomac, and James’ rivers, which appear to be their general 
winter rendezvous. Beyond this, to the south, I can find no cer- 
tain accounts of them. At the Susquehannah they are called Can- 
vass-backs, on the Potomac JF/iite-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 VaUisneria,^ 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 resemblance to small celery. This grass is 
in many places so thick that a boat can with dilFiculty be rowed 
through it, it so impedes the oars. The shores are lined with 
large quantities of it torn up by the Ducks, and drifted up by the 
winds, lying like hay in wind-i'ows. Wherever this plant grows 
in abundance the Canvass-backs may be expected, either to pay 
occasional visits, or to make it their regular residence during the 
winter. It occurs in some parts of the Hudson ; in the Delaware 
near Gloucester, four or five miles below Philadelphia ; and in most 
of the rivers that fall into the Chesapeake ; to each of which par- 
ticular places these Ducks resort ; while in waters unprovided with 
this nutritive plant they are altogether unknown. 
On the first arrival of these birds in the Susquehannah, near 
Havre-de-Grace, they are generally lean ; but such is the abun- 
* The Vallisneria Americana of authors. 
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VOL. VIII. 
