CANVAS-BACK DUCK. 
337 
the Gulf of Mexico, being seen in winter in the mild climate 
of New Orleans. In these different sections of the Union they 
are known hy the various names of Canvas-backs, \V hite- 
backs, and Sheldrakes. In the depth of winter a few pairs, 
probably driven from the interior by cold, arrive in Massachu- 
setts Bay, in the vicinity of Cohasset and near Martha’s Vine- 
yard ; these, as in the waters of New York, are commonly 
associated with the Red-head, or Pochard, to which they have 
so near an affinity. I'heir principal food, instead of the fresh- 
water plant Valisneria, which is confined to so small a space, 
is in fact the different kinds of sea-wrack, known here by the 
name of eel-grass, from its prodigious length. Ihese vege- 
tables are found in nearly every part of the Atlantic, growing 
like submerged fields over all the muddy flats, shallow bays, 
estuaries, and inlets, subject to the access of salt or brackish 
waters. They are the marine pastures in which most of the 
Sea Ducks, no less than the present, find at all times, ex- 
cept in severe frosts, an ample supply of food. 
The Canvas-backs on their first arrival are generally lean ; 
but by the beginning of November they become in good order 
for the table. They are excellent divers, and swim with speed 
and agility. 'I'hey sometimes assemble by thousands in a 
flock, and rising suddenly on wing, produce a noise like thunder. 
During the day they are commonly dispersed about in quest 
of food, but towards evening collect together, and coming into 
the creeks and river inlets, ride as it were at anchor, with their 
heads under their wings asleep ; sentinels, however, appear 
awake and reaily to raise an alarm on the least appearance of 
danger. At other times they are seen swimming about the 
shoals and diving after the sea-wrack, which they commonly 
pluck up, and select only the tenderest portion towards the 
root. 'I'hough thus laboriously engaged, they are still ex- 
tremely shy, and can rarely be approached but by stratagem ; 
for even while feeding, several remain unemployed, and vigilant 
against any surprise. When wounded in the wing, they dive to 
prodigious distances, and with such rapidity and perseverance 
as almost to render the pursuit hopeless. The great demand 
VOL. II. 22 
