1908. 



NATURAL SCIENCES OF PHILADELPHIA. 



145 



I906 



great February movement, and there were no species ready to respond 

 to the favorable conditions in March. 



High temperature on April 5 was accompanied by rain and migra- 

 tion was not apparent until April 6 to 8 when there was an extensive 

 movement. Another occurred on the 1.3th, while the high tempera- 

 ture of April 21 was followed by a wave on the 22d, which was resumed 

 on April 25 after a cold rain. The greatest movements were April 

 29-May 1 , May 3 and May 5. 



1907 



Apr. I Api^-'^ Mof/I. MatftSf 



of falling temperature with frost on the morning of May 12. The last 

 May wave did not occur until the 19th. 



In this season we have an example of the difficulty of characterizing 

 an entire migration as early or late. The beginning of the movement 

 was late, while most of the jMarch dates of arrival were remarkably early; 

 early April migrants were late, but the great movements at the close 

 of the month brought conditions nearly to the normal, while the May 

 migrants were phenomenally late. 

 10 



