Mr Black wall on the Instincts of' Birds. 247 



large families to provide for, are, in their wild state, polygamous. 

 Indeed, it is evident from the anatomical researches of Mr John 

 Hunter and Dr Jenner, that the sexual connexions of birds, 

 and the season at which they breed, depend upon certain condi- 

 tions of their organization, and not upon any information de- 

 rived from experience or instruction. 



The propensity to propagate their species, in this class of ani- 

 mals, is well known to be of periodical occurrence ; and dissec- 

 tion clearly proves, that it is always accompanied by a very per- 

 ceptible alteration in the reproductive system. Besides reclaim- 

 ed birds, under the influence of a plentiful supply of nourishing 

 food, shelter from the inclemency of the weather, and the va- 

 rious stimuli with which domestication is usually attended, may 

 be kept in this state of sexual excitation for several years, with 

 comparatively little interruption. A check to the greatly in- 

 creased activity of the reproductive powers, so induced, is speedi- 

 ly given, however, by a diminution of sustenance and exposure 

 to cold ; at the same time also, a visible change takes place in 

 the physical condition of the organs of reproduction. In the 

 selection of their mates, the feathered tribes are undoubtedly 

 governed by instinct, as there is reason to believe that different 

 species, in a state of nature, never pair together, however near 

 their affinity or general resemblance may be. The rook is not 

 observed to breed with the crow, the titlark with the lesser field- 

 lark or rock-lark, the sedge-warbler with the reed-wren, or the 

 cole-titmouse with the marsh-titmouse. Now, were every indi- 

 vidual left to the unrestrained exercise of its own discretion in 

 a matter of such essential importance, the utmost confusion 

 might be expected to ensue; an unprolific hybrid progeny would 

 be speedily produced, and the total extinction of many species 

 might be the ultimate consequence. But the allwise Author of 

 nature has not suffered the reproduction of his creatures to be 

 liable to such a contingency, but has implanted in the mind of 

 each a powerful predisposition to form sexual unions with its 

 own kind exclusively. Thus the evils which would unavoid- 

 ably result from the indiscriminate intercourse of various spe- 

 cies are effectually prevented. 



It must be admitted that an intermixture of distinct species 

 does sometimes occur among our domesticated birds ; but this 



