208 THE BIRDS OF SHERWOOD FOREST. 
been repeated by every author, from Montagu to the 
present time.* | 
The gallinaceous birds have generally only one gland, 
which, as they do not seek their food upon the water, 
would, according to the common theory, furnish sufficient 
oil for their wants. But surely a dressing of oil, how- 
ever slight, would be a bad preparation for the practice 
of dusting, in which these birds love to indulge. Instead 
of tending to their cleanliness and comfort, it would have 
a contrary effect, dirtying and clogging their feathers. 
And yet we know it is not so; for, after the dust is ex- 
pelled by a few vigorous shakes, their plumage is as 
clean as ever. 
The practice of dusting, which seems merely to be 
employed as a simple mechanical means of dislodging 
the parasites with which all birds are infested, I have 
seen practised three or four times in succession ; and if 
the feathers had been oiled, this repeated application of 
dust would but increase their filthiness. 
While thus rejecting the common notion, I would not 
venture to assert that Iam certain of the true use of 
* “ Nature, ever provident in all her ways, has taken care to supply 
every bird, more or less, with an external secretion of an unctuous 
nature, situated in a glandular bag upon the rump, which they in- 
stinctively make use of for oiling and dressing their feathers as 
occasion requires. In water-fowl this bag is most conspicuous, 
and it is remarkable that birds most frequently use it after washing, 
previously to their feathers becoming perfectly dry.”—Montagu’s 
Ornithological Dictionary, p. 136. “And finally, the gland 
which all birds have at the rump, and from which they express an 
oily matter to preserve their feathers moist, is most considerable in 
those that live upon the water, and contributes to make their plu- 
mage impermeable.’—The ‘Sea and its Living Wonders, by Dr. 
G. Hartwig, p. 123. Longmans, 1860. 
