°89s''J Jokes, Bird Migration in Iowa. 12C 



When the line representing a species begins on the line 

 separating two years, it indicates that the species was present all 

 winter ; and the end of such a line on a line separating two years, 

 indicates that the species remains all summer. In a few cases 

 a species not a summer resident remained longer than the last 

 month indicated on the chart ; its final departure is recorded in 

 figures in the last space for the year, opposite its name. 



The species are arranged on the chart in the order of their 

 average arrival for the five years. If a species, as the Flicker in 

 1890, has been present all winter in very limited numbers in 

 especially favored localities, account is taken only of the first 

 migrating individuals, the dotted line indicating the presence of 

 the few winter birds. When apparent irregularity is evidently 

 due to the scarcity of the species, as in the case of Sparrow 

 Hawk, its position is determined by the three earlier and more 

 regular dates of arrival. 



Bird movements are profoundly influenced by the weather. 

 With the charts illustrating the bird movements before us, and 

 a parallel running account of the weather, we shall be enabled 

 to see the force of this influence. 



During the five years from 1886 to 1890 inclusive, January 

 opened very cold with more or less snow, and continued cold, 

 with a few warm clays, closing with below zero weather every 

 year except 1890. This year a thaw began on the 27th of the 

 month and ended February 7, after taking away ten inches of 

 snow. 



With the one exception of 1890, February also opened cold 

 and snowy. In 1886 there was a warm period beginning on the 

 6th and closing on the i8th, followed by six cold days with north- 

 west winds. The month closed very warm. In 1887 there was 

 no warm period of any consequence during the whole of the 

 month. But in 1888, after two weeks of continuous cold weather, 

 there were three moderately warm days centering on the 13th, 

 and another short period of warmth from the 2 2d to 24th, the 

 month closing cold. In 1889 there was a slight thaw on the 21st, 

 and another on the 28th, but the ground was bare during the last 

 half of the month, with no severe weather. The remarkable 

 warm period of 1890. ending February 7, has already been 



