DELAWARE VALLEY ORNITHOLOGICAL CLUB. 61 



1907. 1906. 1905. 



Phoebe Mar. 15-17 (14) Mar. 29-Apr. ti (12) Mar. 16-19 (16) 



Chipping Sparrow. Mar. 27-29 (21) Apr. 5-8 (Mar. 24) Mar. 26-28 (18) 



In April and May we have to deal with migrants which start 

 their flight for the most part in the tropics far south of the 

 United States, and are of course not affected bj' temperature 

 conditions prevalent here until they reach the region affected. 



Taking the forty species of April and May migrants, of which 

 we have the fullest records, we find by comparing the earliest 

 arrivals within the Philadelphia district for 1907, 1906 and 1905 

 that 16 species were earlier in 1906 than in 1905; 16 earlier in 

 1905 than in 1906, and 8 arrived on the same day; the average 

 date for the forty being almost the same for the two years. 



1907, however, compared with 1906 shows 18 species earlier 

 and 21 later; average for forty species one and a half day.« late. 

 Compared with 1905, 15 species arrived earlier, 23 later; average 

 for forty species one day later. 



This is a very slight difference, and has probably little or no 

 significance so far as the movement of the bulk of each species 

 is concerned. As the most accurate means of comparing the 

 latter, we have ascertained the date upon which each species 

 had been reported from at, least one-half of the stations at which 

 it was observed. This gives a fair basis of comparison between 

 two seasons, in one of which the migration may have been 

 spread over a number of days, while in the other it was concen- 

 trated upon a few. 



For example, the Brown Thrasher was first observed at our 

 various stations during 1907, 1906 and 1905 as follows, the 

 numbers in parentheses indicating the number of stations at 

 which it was reported if at more than one : 



1907. March 13, 17; April 20, 23, 25, 26 (6), 27 (7), 28(2), 

 29 (2), 30 (2). 



1906. March 9; April 10, 16, 17 (2), 19 (3), 20, 21 (4), 



22 (3), 24 (2), 25 (2), 26, 27, 28 (2), 30. 



1905. April 9, 13, 14 (2), 16, 18 (2), 19 (2), 21 (2), 22 (6), 



23 (3), 24 (4), 25 (2), 26, 29, 30. 



It had thus reached at least half the stations as follows : 



1907, April 27; 1906, April 21; 1905, April 22. 



