BRITISH WARBLERS
intrusion upon, and apparent desire to be a spectator of, the quarrels and tragedies in the bird life of the surrounding district, so inseparable from the habits of the Chiff-chaff. At the same time it is not likely that it is altogether absent, but it is safe to say that it is by no means present in a similar degree, for whereas the inquisitive nature of the Chiff-chaff is constantly forcing itself upon our attention, that of the Willow Warbler has to be sought for, and can only be observed with difficulty, which of itself is evidence of considerable difference in the character of the two species.
The vocal powers are more highly developed than those of the Chiff-chaff. The song is unusually plaintive and sweet, appealing to some ears in a manner in which no other song is capable of doing. This is not difficult to understand, for in a wood inhabited by a number of different individuals the constant singing in reply to one another results in a concert which no one could fail to enjoy. When in full song early in the spring the bird utters its complete song from five to seven times a minute, and continues often for many minutes in succession without a pause, but when busily engaged in searching for food its song is heard more intermittently. Between the song of different individuals there seems to my ear to be a certain amount of variation, but I do not feel competent to judge wherein exactly it lies, although the difference often appears to be connected with the pitch; and I am not at all sure that the same individual does not at times vary its song, in addition to its frequent habit of commencing in the middle and leaving out the higher notes. The song really consists of so few notes and the difference between the notes is so slight, that any attempt to resolve it into its constituent parts is very difficult. In different localities there is considerable variation, which is in a great measure due to alteration in the pitch. On the west coast of Ireland, for instance, the tone is deeper, whereas in Hungary it is higher, and, to my ear at least, not so pleasing. In addition to the song there are sundry call notes, and the most common one to which I have
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