AQUATIC FOWL. 175 



two feet in length, by three feet in extent, and when in the best 

 order,, weighs three pounds and upwards. The podiard, according 

 to Latham and Bewick, measures nineteen inches in length, and 

 thirty in extent, and weighs one pound twelve or thirteen ounces. 

 " The canvas-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, 

 Powtomac, and .James's 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 Potowrnac, white-backs ; and on James's 

 Eiver, 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 resemblance 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 occurs in some parts of 

 the Hudson ; in the Delaware, near Gloucester, a few miles below 

 Philadelphia ; and in most of the rivers that fall into the Chesa- 

 peake, to each of which particular 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- 

 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 thun- 

 der. They float about these shoals, diving and tearing up the 

 grass by the roots, which is the only part they eat. They are 

 extremely shy, and can rarely be approached, except by stra- 



