22 
THE BIRDS OF WISCONSIN. 
Aytliya vallisneria (Wils.J. CANVAS-BACK. 
Common migrant. Thirty to forty years ago this duck was 
supposed to remain only a few days in early spring and 
October in favored localities where the so-called "wild celery" 
grew in abundance. Such localities were apparently not 
numerous, and the species was rated as one of exceedingly 
irregular distribution. During the past twenty-five years it 
has become more universally distributed over the state, and 
locally, at least, not greatly diminished in numbers. We have 
known for a number of years that the so-called "celery buds" 
with which these and other ducks are actually crammed to 
the bill, was no part of the plant Vallisneria spiralis, but still 
we were unable to determine what it was. What little we do 
know in this connection is due principally to the careful obser- 
vations of Mr. H. L. Skavlem, of Janesville. Mr. Skavlem 
took the "buds" from the oesophagus of freshly killed specimens 
of the canvas-back, and keeping them in water in the cellar 
through the winter, succeeded in growing the entire plant the 
next season. This plant proved to be one of the pond-weed 
family (Naiadaceae), of which there are numerous species in 
the northern states. These gemmae, or nutlets comprise the 
great bulk of the food of this duck in October and November 
in Wisconsin. In shape they are spindle form, from one-half 
to one inch or more in length, of a whitish color and highly 
farinaceous. The pond-weed grows very luxuriantly in Lake 
Koshkonong and other waters of the state. Where the 
"celery" (Vallisneria spiralis) grows in abundance they no 
doubt eat parts of it, but this condition does not obtain in 
quantities sufficient to furnish food enough to tempt the ducks 
to remain. The unusually hot, dry summer of 1901 made the 
shallow water of Lake Koshkonong almost hot, and the pond- 
weed, as well as other aquatic plants suffered greatly, so that 
the nutlets were smaller than usual and much fewer in number. 
As a consequence the ducks remained a much shorter period 
than usual. It is our opinion, in which Mr. Skavlem concurs, 
that this particular pond-weed is found in greater abundance 
than formerly. It also grows in shallower water than the 
Vallisneria, often even inside the belt of rushes. There is not 
. a shadow of doubt but that the bulk of the canvas-back's food 
consists of the nutlets of this plant at the present day, but has 
anyone noted any difference in the flavor of the flesh? A 
number of crippled birds remain on Lake Koshkonong 
through the summer, and we know of three instances of 
females being seen with nestlings, but incline to the opinion 
