PREMATURE NESTLING. 367 
ments which favour the opinion I have here advanced. 
There are probably some species which sing under 
the influence of amorous excitation of the spirits 
more decidedly than the rest of birds, and the facts 
(such as those recorded by Montagu) appearing to 
support this have originated the hasty deduction 
regarding the whole class, that love was the sole 
reason of song ; but while the Nightingale exhibits 
so strongly the result of this power on his spirits, 
the Woodlark his competitor sings deliciously at 
periods during all seasons. Although then a mys- 
tery and degree of doubt prevent a ready inference on 
the subject, there seems room to conclude that several 
stimuli act on the animal spirits of the feathered 
tribes and in the case of song-birds induce their 
melodies,—that though in them there is no love 
withont song, there may be song without love. 
As connected with the above statements, I pro- 
pose now to enquire whether a forward state of 
spring can induce a disposition to pairing before 
the usual time, besides inducing song at an unusual 
early period. Food is known to induce amorous 
feelings in domesticated birds at very early periods, 
and it therefore remains to be seen whether weather 
is of equal importance. It would seem at first par- 
ticularly unlikely that the period of nestling should 
be anyway interfered with, it appearing so rational 
to conclude that an express time has been ordered 
for every species, and that this is immutable; yet 
there is ground to believe that the incubating period 
may be both deferred and prematurely induced in 
accordance with the character of weather at the 
opening of the year. I have already expressed 
a suspicion that such might be the case, but as 
yet I have advanced no proofs on the subject lest 
I might rather obscure the argument I have just 
quitted by connecting together the exclusive ques- 
tion of song with that of nestling accompanied 
