210 THE BIRDS OF SHERWOOD FOREST. 
These birds are more thoroughly aquatic than any others, 
seeking their food entirely under water; and, if the 
received theory is true, they would require much oil to 
keep their plumage waterproof, notwithstanding the 
scale-like character of some of the feathers; and yet, 
strange to say, they do not possess the vestige of an oil 
gland, and they, consequently, have no means of “ oiling 
their plumage.” 
I had some correspondence with Mr. Zurhorst, the 
eminent poultry breeder of Dublin, on this subject, who 
considers from his observations on his domestic ducks, 
that they do, or at least appear to, apply the oil which they 
obtain from the gland, to their feathers. He says, “ At 
all events the feathers around the glands are raised on 
end, the bill is buried in them, accompanied by a jerk- 
ing motion expressive of pressure or squeezing being 
used on some special part or parts; this is followed by 
repeated applications of the bill to the different parts of 
the plumage—not at random, but going carefully over 
the surface, inch by inch. My Aylesbury ducks, after 
long confinement, when fattening for exhibition pur- 
poses, when turned out on the pond for the first time, 
are evidently loose-feathered; the plumage becomes 
speedily saturated, and, if the birds are at once confined 
again, takes very long to dry; whereas if, after being 
allowed time to dry and dress their feathers, they are 
turned in again, they come out apparently as sleek and 
impervious to wet as ever they were. I would incline 
to think that if the oil were supplied by an involuntary 
operation through the body itself, there would be no 
deficiency in the supply during confinement. With 
reference to gallinaceous birds, the dusting process 
strikes me more as a cleansing process than specially 
