v,,i 1 ,,^ X CCM Kl . -ation toil 2] 7 



has the smallest variation in its time of arrival of all the birds that 

 were recorded at Lanesboro. 



In the matter of the total amount o\ heat received in the spring 

 the variations are 30 percent whether estimated from the first ot 

 .January or from the first o( March, moreover the largest variations 

 from 22S3 in 18S8 to 3060° in L889 occur with but a single day 

 difference in date of arrival. The same result is obtained if the 

 date of appearance is compared with the total heat received in 

 the vicinity ol Dubuque, eighty miles south o( Lanesboro, or at 

 Davenport, a hundred and fifty miles farther south, though the 

 percentage variations are not so great, that at Davenport being 

 only 15 percent. 



Parenthetically it ma\ be remarked that the temperatures during 

 the winter ami previous to March 1 have seemingly no effect on 

 plant or animal growth ami it is the degrees of heat after March 1 

 that determine the advance of the season. This was strikingly 

 shown at Washington, D. C, the spring of 1912, when after a winter 

 of unusual severity in January ami February, the growth of plants 

 became fully up to normal as soon as the heat after March 1 had 

 risen to its normal ami long before the total heat counted from 

 January 1 had reached the average. The bird arrivals averaged 

 earlier than usual notwithstanding the cold winter. 



The variations in the time of the arrival of the bird from year to 

 year i\o not agree with the variation of the season. The spring 

 oi L889 is the warmest. March and April together, at all three 

 places; indeed that spring is one o'i the warmest the Mississippi 

 Valley has ever known, but the Oriole does not arrive so early this 

 year as the average of the ten years, but little relation can be 

 traced between the changes in temperatures and the changes from 

 year to \ ear in the time of arrival. It is true that in L893, w hen the 

 Oriole arrived at its latest date Max 6 the temperature is 

 the coldest at all three places, and in 1SS7 when the date of arrival 

 is the earliest May I the temperature is also the highest at 

 all three places. But here the agreement ends, for the Oriole also 

 arrives on May 6 in the years 1884, L885, an.! 1SSS, that are both 

 cold and warm years and on May 2 in 1890 that is among the colder 

 years. 



During spring migration the direction of the wind seems to have 



