33 THE ARCHITECTURE OF BIRDS. 
rough mattress the female eider spreads a bed of 
the finest down plucked from her own breast, and 
by no means sparingly, but, as Brunnich informs us, 
heaping it up, so as to form a thick puffed roll quite 
round the nest. When she is compelled to go in 
quest of food after beginning to sit, she carefully 
turns this marginal roll of down over the eggs to 
keep them warm till her return. It is worthy of re- 
mark, that though the eider-duck lays only five or six 
eggs, “it is not uncommon to find more than even 
ten and upward in the same nest occupied by two 
females which live together in perfect concord ;”* 
a circumstance, however, of which we shall meet 
with other instances as we proceed. 
The quantity of down in each nest is said by Van 
Troil to be about half a pound, which, by cleaning, 
is reduced one half. By Pennant, who examined the 
eiders’ nests in the Farn islands, off Northumberland, 
it is only estimated, when cleaned, at three quarters 
of an ounce, and this was so elastic as to fill the crown 
of the largest hat.t The difference of quantity in 
these two accounts, theoretically ascribed by the 
translators of Buffon to difference of climate, may 
have arisen from the one being the first, and the 
other the second or third nest of the mother duck : 
for if the first nest be plundered of its down, though 
she immediately builds a second, she cannot furnish 
it with the same quantity as before; and, if forced 
to build a third time, having then stripped her breast 
of all she could spare, the male is said to furnish 
what is wanting, which is recognised as being con- 
siderably whiter than the female’s. When the nest 
is not robbed, it is said that he furnishes none. 
The extraordinary elasticity of the down appears 
from the fact we have mentioned of three quarters 
of an ounce filling a large hat. It is worthy of no- 
tice, however, that it is only the down taken from 
* Van Troil’s Letters on Iceland. 
+ Pennant, Tour in Scotland, 8vo. edit., p. 36. 
