CANVAS-BACK DUCK. 341 
The Canvas-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 neighbourhood of 
the Chesapeake Bay, particularly the Susquehannah, the Pa- 
tapsco, 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 Canvas-backs, on the Potowmac White-hacks, 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 
that a boat can with difficulty 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 rows. Wherever this plant grows in abundance the 
Canvas-backs may be expected, either to pay occasional visits 
or to make it their regular residence during the winter. It oc- 
curs in some parts of the Hudson; in the Delaware near Glou- 
cester, a few miles below Philadelphia; and in most of the rivers 
that fall into the Chesapeake, to each of which particular places 
these Ducks resort; while in waters unprovided with this nutri- 
tive 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- 
dance of their favourite food, that towards the beginning of 
November they are in pretty good order. They are excellent 
divers, and swim with great speed and agility. They sometimes 
assemble in such multitudes as to cover several acres of the 
river, and when they rise suddenly, produce a noise resembling 
