April the i8th, I had told you peremptorily that I 

 knew your willow-lark, but had not seen it then : but 

 when I came to procure it, it proved, in all respects, 

 a very Motacilla trochilus ; only that it is a size 

 larger than the other two, and the yellow-green of 

 the whole upper part of the body is more vivid, and 

 the belly of a clearer white. I have specimens of 

 three sorts now Ivino^- before me, and can discern 

 that there are three gradations of sizes, and that 

 the least has black legs, and the other two flesh-col- 

 oured ones. The yellowest bird is considerably the 

 largest, and has its quill feathers and secondary 

 feathers tipped with white, which the others have 

 not. This last haunts only the tops of trees in high 

 beechen woods, and makes a sibilous grasshopper- 

 like noise, now and then, at short intervals, shivering 

 a little with its wings when it sings ; and is, I make 

 no doubt now, the Reguliis non cristatus of Ray ; 

 which he says " cantat voce stridula locustae." Yet 

 this great ornithologist never suspected that there 

 were three species. 



Selborne, Aug. 17, 176S. 



* Hedge-warbler (see Letter XXVI.) : Sylvia loqiiax, black legs ; 

 Sylvia trochilus^ yellowish belly ; Sylvia sibilatrix, white belly. 



75 



