ISOLATION 183 



they are very closely related, though not included in the same 

 genus. All of them have a very distinctive song, and none of 

 them, unless we except the blackcap and the whitethroat, have 

 anything at all striking about their plumage. 



With the song of the marsh-warbler and reed-warbler, which, 

 as their names suggest, have very similar haunts and are often 

 found together, I am unfortunately not familiar. But they are 

 said to be easily distinguishable. That is certainly the case with 

 the songs of the blackcap and garden-warbler whatever may 

 have been said and written to the contrary. Generally speaking 

 the Warblers may be described as a plainly coloured set, which, 

 but for their song, would be very easily confused. It must be 

 owned that there are exceptions : the Barred-warbler, whose 

 plumage is unmistakable, is said to sing nearly as finely as the 

 Garden-warbler. The Bluethroat (Cyanecula suecica), whose skin 

 could easily be picked out from thousands of skins of small 

 birds flung into a chaotic heap, so unapproached is the character 

 of its plumage, has a very rich song, rivalling, it is said, even 

 that of the nightingale. However, there are two forms of Blue- 

 throat, the one with a white, the other with a red spot in the 

 middle of the blue, and this colour distinction may serve to keep 

 apart two forms whose notes are nearly or exactly alike. And 

 seeing that the Warblers, if we count among them a number of 

 closely allied birds that are not actually put in the same genus, 

 are so many more than I have mentioned, it is not wonder- 

 ful that recognition marks, appealing to the eye, have in some 

 cases been developed in addition to characteristic notes. The 

 two methods of distinction are not antagonistic though they are 

 often alternative. Among the pipits, again, we have several 

 nearly resembling each other in plumage, but whose notes are 

 quite unlike. Such are the tree, rock, and meadow pipits. 

 (Anthus trivia/is, obscurus and pratensls}. The same thing holds 

 true, to a great extent, of the larks. Passing now to the con- 

 verse proposition we find a number of common tits, the great, 

 blue, marsh, coal, crested, long-tailed (Parus major, caruleus, 

 palustris, ater, cristatus and Acredula caudata), very distinct in 

 their plumage, but so difficult to discriminate by their songs that 



