pintails, nor to account for the complete departure of 

 teals, widgeons, gadwalls, and diving ducks. 



Analysis of Effect of Weather on Migration. -The 

 effect of weather in initiating the mass waterfowl mi- 

 gration of October 31-November 1, 19.'i5, is evaluated 

 as follows: Low pressure areas in Canada resulted in a 

 southward flow of a mass of Continental Arctic air. The 

 low temperatures resulting from Continental Arctic air 

 triggered the flight from the Great Plains of Canada and 

 the United States. The flight moved faster than the cold 

 air mass, so that at Winnipeg, Manitoba (where a sta- 



tionary front slowed the southward flow of cold air), the 

 migration of waterfowl was in advance of the Arctic air. 

 Because of a swinging gate action of the Arctic 

 air, which pivoted around a low pressure area in south- 

 western Manitoba, the waterfowl flight arrived at Minne- 

 apolis with the cold front. By the time the flight reached 

 Peoria, Illinois, it was again in advance of the \rctic 

 air. The southward movement of cold air accelerated 

 between Peoria and Memphis, Tennessee, so that part 

 of the waterfowl flight arrived at Memphis before and 

 part of it with the cold air. 



LITERATURE CITED 



Bennett, Holly Reed 



1952. Fall migration of birds at Chicago. Wilson Bui. 64(4): 197-220. 

 Devlin, Joseph M. 



1954. Effects of weather on nocturnal migration as seen from one observation point at Philadelphia. Wilson 

 Bui. 66(2):93-101. 

 Dennis, John V. 



1954. Meteorological analysis of occurrence of grounded migrants at Smith Point, Texas, April 17-\Iay 17, 

 1951. Wilson Bui. 66(2):102-11. 



Hochbaum, H. Albert 



1955. Travels and traditions of waterfowl. University of Minnesota Press, Minneapolis. 301 pp. 

 Raynor, Gilbert S. 



1956. Meteorological variables and the northward movement of nocturnal land bird migrants. Auk 73(2):153- 



75. 

 Smith, Harry R., and Paul W. Parmalee 



1955. A distributional check list of the birds of Illinois. 111. State Mus. Pop. Sci. Ser. 4. 62 pp. 



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