7o iim? CX 1 Cookh, The Relation of Bird Migration to tht Weather. 205 



THE RELATION OF BIRD MIGRATION TO THE 

 WEATHER. 



in w ills \v. COOK] 



Tn i belief is quite general thai there is a close connection between 

 the weather and bird migration; thai it' the weather is nol the 

 cause of migration, il is ;ii leasl the mosl Important, indeed the 

 m>\ erning, factor in determining the time of the bird's arri\ ;il, and 

 particularly in causing tin' variations From year to year. The 

 intimate relation supposed i<> exisl between the weather and the 

 bird's movements is thus promulgated by ;i very acute migration 

 observer \\ li<> wrote me: " I have collected such ;i large number of 

 dates for mir common birds thai il' you give me ;i good accounl of 

 the weather conditions, I can give you the dates of arrival and 

 movements of many species withoul going into the field." After 

 an exhaustive study and comparison of bird arrivals with the 

 accompanying weather, the results were found to be so utterly al 

 variance with the above quoted opinion, thai t hey were summarized 

 as follows: "The weather encountered en route influences migra- 

 tion in a subordinate way, retarding or accelerating the birds' ad- 

 vance bj onl\ a lew da,\ l and having slighl relation to the dale 

 of an i\ a I at the nesting site. Local weather conditions on the day 



of arrival at an\ given locality .-ire minor factors in determining 

 the appearance oi a species at that place and time. The major 



factors in the problem art- the weather conditions far to the south- 

 ward, where the night's flighl began, and the relation which that 

 place and time hear to the average position of the bird under 

 normal weather conditions." 



The above quotation is from an article that was written for the 



yearbook of the Departmenl of Agriculture for L910. In its 



necessarily condensed form, there was opportunity for nothing 



more than a mere rtatemenl of conclusions, wit horn anj of the data 



on which those conclusions were based. It seems advisable that 

 a J nopsis of the more important of these data should he published 



a . a contribution to knowledge of the phenomena of bird migration. 



For the solution of the proposed problem it is necessary to have 



the notes of a thoroughly reliable and competent observer, who is 



