Mr Blackwall on the Instincts of Birds. 245 



thai wagtails and hedge-warblers feed the young cuckoos they 

 bring up, long after they leave the nest, whenever they hear 

 their cuckooing, which, on the authority of Linnaeus*, he states 

 to be their cry of hunger, he was induced to adopt the same 

 opinion respecting their calls. Now, whether the song of the 

 nightingale results from education, as Kircher maintains, or 

 whether it is wholly independent of tuition, I have never had 

 any direct means of deciding, as the bird is only an accidental 

 visitor in this part of the kingdom. From unexceptionable jCX- 

 periments, however, made with the greatest care, on several 

 other species of British singing-birds, I have no hesitation in 

 affirming, that the peculiar song of each is the natural conse- 

 quence of an instinctive impulse, combined with a suitable state 

 of the vocal organs. This latter condition deserves particular 

 attention, for it is a fact, which has been very generally over- 

 looked, that most of our songsters are absolutely unable to con- 

 tinue their melodious strains beyond the latter end of July, or 

 the beginning of August ; the strenuous but unavailing exer- 

 tions they make to prolong them, sufficiently proving their si- 

 lence not to be a matter of choice, but of necessity. This cir- 

 cumstance, together with the extreme difficulty they experience 

 in recommencing their songs in spring, clearly demonstrates, that 

 their delightful warblings depend upon the energy of those mus- 

 cles which contribute to form the voice; an energy which ap- 

 pears to be influenced chiefly by food, temperature, and the ex- 

 ercise of the reproductive functions; for, by due attention to 

 the regulation of these particulars, the vocal powers of caged 

 birds may be called into action^ or circumscribed at pleasure. Of 

 this, persons who have the management of breeding canaries 

 may easily satisfy themselves ; and female birds, in a state of 

 captivity, when brought into high condition, are known, occa- 

 sionally, to assume the song of the male. That Jonston must 

 have been deceived in supposing he heard the nightingale in 

 Scotland, is evident, as it is well known that this warbler is ne- 

 ver found north of the Tweed, in Great Britain. It has been 

 ascertained, too, contrary to the opinion of Linnaeus, that young 

 cuckoos, before they come to maturity, utter a feeble cry only ; 

 they cannot, therefore, acquire the calls of their species while 

 • Sy sterna Naturae. 



