o2 Fry, Seasonal Decline in Bird Song. [jaii. 



summer caused an earlier decline than usual, or if a warmer season 

 retarded the diminution. 



The accompanying chart is a graphical presentation of the data 

 given in this paper, showing the decline of bird song, for thirty-seven 

 species, studied at Cold Spring Harbor, from July 1 to August 10, 

 1914. It will be seen that this chart is on the same plan as the one 

 described above. The forty-one vertical columns represent the 

 days of the period studied, and each wide horizontal line (taking 

 the place of the notes on the horizontal columns) by its varying 

 width indicates the song decline of a species. The birds have 

 been arranged according to the date when the depression begins, 

 the one affected first, being placed at the head of the list. The 

 heavy black portions of the lines indicate maximum volume of 

 song, and obliquely lined portions represent the days of lesser 

 quantity. The volume of song of one species as compared with the 

 volume of another is not taken into consideration at all, for the 

 Song Sparrow {Mclospiza viclodia mclodia) which was heard almost 

 constantly, and the Meadowlark {Sturnclla mcupia magna) which 

 sang only occasionally, are both represented by black lines of the 

 same width so long as they continue to sing at their maximum, 

 which is up to July 21. After that date the narrowing lines show 

 their decline, but there is absolutely no indication as to the relative 

 volume of song between the two species. 



At the end of the paper are several lists summing up the results. 

 One of them contains those birds, concerning which manifestly 

 insufficient data have been gathered, and another summer's study 

 might show different results for some of these species. It must be 

 remembered that the studies did not begin till the first of July, 

 and if any of the birds commenced to decline prior to that date, 

 the fact could only be surmised. Surely the majority were in 

 full song at that time, and only further study, beginning in June 

 will clear up the doubtful cases, which have also been listed. 



The Robin (Planesticus migratorius migratorius) was heard con- 

 tinually during the first few days of July but a scarcely perceptible 

 decline of song began as early as the seventh. In fact, had it been 

 carefully studied from the middle of June, the song volume of July 

 1, in comparison with that of the preceding weeks, even then might 

 have shown the first faint signs of diminution. In all probability 



