INSTINCTS OF BIRDS. 265 



In the selection of their mates, the featliered 

 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 fieldlark or 

 rocklark, the sedge warbler with the reed wren, 

 or the cole titmouse with the marsh titmouse. 

 Now, were every individual left to the unre- 

 strained exercise of its own discretion in a matter 

 of such essential importance, the utmost confu- 

 sion 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 reproduc- 

 tion of his creatures to be liable to such a con- 

 tingency, 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 unavoidably result from the indis- 

 criminate intercourse of various species are effec- 

 tually prevented. 



It must be admitted that an intermixture of 

 distinct species does sometimes occur among our 

 domesticated birds ; but this deviation from their 

 ordinary instinct is rare, and may, with great 



2 L 



