Ferry — On Spring Migration. 27 



THE SPRING MIGRIATION OF 1907 IN THE 

 VICINITY OF CHICAGO. 



BY JOHN F. FERRY. 



The weather ''"prevailing during March, April, and May of 

 1907, was so abnormal in character that the study of bird- 

 migration during these months was one of absorbing interest 

 to the ornithologist. March, 1907, was a very unusual month, 

 it being the warmest on record for this vicinity, with one ex- 

 ception. Its mean temperature was 43°, which made it 

 actually average 3 degrees warmer than the following April. 

 The average daily temperature was 7.6 degrees warmer than 

 the normal temperature for this month. The month was 

 humid, cloudy and inclement, there being nine days when 

 there was hail, sleet, fog, or thunderstorms and during the 

 month there were but three days of continuous sunshine. 

 Notwithstanding these unfavorable elements bird-life was 

 abnormally abundant from the 16th day on, from which day 

 almost continuous warm weather prevailed. This indicates 

 that temperature is a very important factor in influencing 

 migration. 



April was quite the opposite of March, it being the 

 coldest April on record with one exception. The mean tem- 

 perature of the month was 40° as compared to a normal 

 temperature of 46°. The average daily temperature was 6^^ 

 degrees cooler than the normal. There were but seven clear 

 days during the month. May was peculiar, it being the cool- 

 est May on record (one exception). Its average tempera- 

 ture was 52°, while the normal temperature for May is 56°. 



The corresponding influence of these peculiar weather con- 

 ditions upon bird-migration was quite noticeable. The first 

 half of March was cool, the temperature averging 35° up to 

 the 16th, when the first movement of the year really began. 

 During the remainder of the month the temperature averaged 

 50°, and beginning with the large movement on the 16th bird 



* Professor Heury J. Cox, of the local U. S. Weather Bureau, has 

 beeu extremely kind in furnishing me with full reports on the 

 weather. The records of the Chicago station extend over 37 years. 



