30 ON THE NOTES OF BIRDS. 
though very limited and imperfect, still answers many 
important purposes, and contributes materially to the 
happiness and preservation of species. Thus birds 
which congregate and which live in society have 
usually a regular watch stationed in some command- 
ing situation, whose note of alarm is understood by 
the whole community. Of the truth of this obser- 
vation, Fieldfares and Rooks furnish familiar and 
striking instances. The shrill call of the Swallow, 
the harsh scream of the Jay, and the petulant cries of 
the various species of Titmouse likewise intimate the 
approach of an enemy. The reiterated cackle of the 
Domestic Hen after she has laid speedily announces 
the joyful event; her cluck indicates that she has 
become the mother of a family ; by a peculiar call she 
informs her brood whenever she discovers any thing 
suitable for food ; and her shriek is a warning against 
impending danger. What is usually called the prating 
of poultry is expressive of satisfaction and compla- 
cency: but it is needless to multiply examples or to 
insist further on the many sueful purposes to which 
a familiarity with the language of birds may be ren- 
dered subservient. It will suffice to remark that this 
knowledge supplies the means of making fresh dis- 
coveries, of correcting numerous errors, and of re- 
moving many of those doubts and difficulties which 
have arisen from the great similarity of some species, 
and the peculiarities incidental to age, sex, and a 
change of food or climate in others, without placing 
