j*gi3 I Cooke, Tfu Relation of Bird Migration to the Weather. 219 



from Cuba. One would expecl these birds, if any, to wait for a 

 favoring wind before starting to sea, bu1 the records indicate thai 

 tiny pay no attention to the direction of the wind. II' the birds 

 preferred :i south wind, there should be ;i large number of arrivals 

 during south wind periods, or if they disliked ;i head wind, there 

 should be only a few north wind records. As a fad neither of 

 these conditions is found and the percentage of migration with a 

 south \\ ind is no greater than the average percentage of south wind 

 thai occurs there during the spring months, and the birds fly 



directly againsl a north wind as often proportionally as worth 

 winds occur. 



Spring migration consists of a series of rapid advances followed 

 li\ days of inactivity or possibly of retrogression. After a check 

 to the northward movemenl and a period <>f rest, when the nexl 

 advance occurs, il docs nol merely proceed far enough to make up 

 for the lost time, bu1 the birds are <piite ap1 to make a long flight 

 forward until they are in ad\ ance of their normal position. 



^. striking example occurs in the migration notes from Lanesboro, 

 Minnesota. During the spring of inns, the temperature dropped 

 on March 22, thirty-four degrees below the normal and migration 

 was suspended for about two weeks. 'I ne temperature rose gradu- 

 ally and when the warmth was almost to normal on April I, a 

 greal arrival of birds occurred. The Phoebe, Bronzed Grackle 



and Killdeer appeared after a delay of five, four, and three days 



respectively; the Song Sparrow was present just on time, while 



the Fox Sparrow was three days in advance of his usual date, the 



Brown Creeper four days, the Ruby-crowned Kinglet, Yellow-bel- 

 lied Sapsucker, Field Sparrow and Purple Martin, seven, nine, 

 nine, and leu days earlier than usual. This early arrival is the 

 more strange in this particular case, because the temperature, 

 while it rose decidedly, did not quite reach normal, SO that these 

 last six species flew far north at an early day and during cold 

 w eat her. 



It seems probable thai in such cases some abnormally warm 

 Weather to the south of the place of arrival is the real cause of the 

 phenomenon, hut in the present instance one must look far south 

 for the warm wave. The course of the weather during the three 



days previous is shown in the accompanying chart. Lanesboro 



