14 \\"arbli':r songs. 



I doubt if a hard and fast line can be drawn between the 

 two stj^es of song-, and I question if even now there are not 

 some species whose call songs are not growing toward the pas- 

 sion song. Certainly some show a tendency in that direction, 

 both in the modification of the notes of the song and the man- 

 ner of utterance at stated times or under peculiarly favorable 

 conditions. Some species manifestly employ the call song for 

 love making without much modification. When the song is 

 given during the chase after the female it is uttered in the 

 throat or only faintly warbled b}' many species, as tho the at- 

 tention could not be divided between the flight and the song, 

 each needing it all. 



The writer knows of only a dozen species who have a fairly 

 distinct passion song. Preeminent among these stands the 

 Oven-bird, so often mentioned above. It is not likely that 

 these are all that sing so, since nearly every year hitherto has 

 seen the list swelled. I would not be bold enough to say that 

 all Warblers sing a passion song that is unlike the call song, 

 but there can be Itttle doubt that more than this dozen should 

 be found to. 



VARIABILITY IN THE CALL SONG. 



To the most of us a Yellow Warbler is a Yellow Warbler 

 be he number one or number one thousand in the list of indi- 

 viduals. We recognize no difference in the different individu- 

 als of a species in any limited region where we study. And 

 it is true that the individual differences of color pattern, while 

 sufficiently unlike to make a mistake among the birds them- 

 selves as to which is their mate unlikely, are practically alike to 

 us. But it is not so iiniversall}^ true with the songs. A singer 

 is not confined to one style of utterance, even under like condi- 

 tions. I meali many species are not, possibly all. But some 

 are far more variable than others. A common variation lies 

 in shortening or lengthening the usual song by dropping or 

 adding syllables. Another common method is the change of 

 position of syllables that are somewhat different, or a change 

 of accent. Sometimes a single syllabled song ma^^ become 

 double syllabled, or vice ver.'-a. The closing cadence may 

 either rise or fall at the pleasure of the singer. But these va- 

 riations do not much affect the character of the song, nor 



