122 ON THE INSTINCTS OF BIRDS. 
It is not, let me remark, intended to insinuate that 
birds are incapable of attainmg any knowledge of 
each other’s notes, since our Domestic Fowls, in many 
instances, are certainly enabled, by observation and 
experience, to connect vocal sounds with the ideas 
they are designed to convey *.. The House-Martin, 
also, readily learns to distinguish the Swallow’s call 
of alarm; and the Ringed Plover, Sanderling, and 
Dunlin, when associated together, evince, by the 
promptitude and exactness with which they perform 
their various aérial evolutions, that they comprehend 
one general signal. All that is meant to be insisted 
upon is, that the notes peculiar to every species, in a 
state of nature, are instinctive. This I have endea- 
voured to prove, in an essay on the Notes of Birds 
(supra, p. 26), by showing that even such individuals 
as are brought up in situations where they have no 
opportunity of being instructed in their appropriate 
notes, do nevertheless utter them naturally. 
The pairing of wild birds, and the period at which 
they prepare to perpetuate their species, aré deter- 
mined, according to Dr. Darwin, by the acquired 
knowledge that their joint labour is necessary to pro- 
cure sustenance for a numerous progeny, and that 
* When our Domestic Cock gives notice to his mates that he 
has discovered some choice morsel of food, the Turkey-hens 
always hasten to secure the delicacy, which the gallant Chanti- 
cleer suffers them to take, even out of his beak, without the 
least molestation. 
