.'52 The Wilson Bulletin — No. 98 



exceptionally favorable circumstances that it is very rarely pos- 

 sible for even the best-trained field ornithologist to identify 

 positively, by the use of glasses, a Bronzed Crackle in the 

 range of the Purple. Also we have grave doubts as to the 

 "Wilson's Warblers" Mr. Kohler records as breeding in New 

 Jersey ('The Oologist," vol. xxxiii., No. 6, p. 104), as Wil- 

 son's Warbler has not been found in New York in summer 

 and is rare in the nesting season even in northern New Eng- 

 land. 



THE CORRELATION BETWEEN THE MIGRATORY 

 FLICHTS OF BIRDS AND CERTAIN ACCOM- 

 PANYING METEORLOGICAL CONDITIONS.^ 



FRANK SMITH. 



The purpose of this paper is to call attention to the correla- 

 tion between the principal migration activities of birds in 

 Spring in Central Illinois and certain types of weather con- 

 ditions. The existence of such correlation is shown by an 

 examination of the migration records which have been made 

 during the past fourteen years (1903-1916) at the University 

 of Illinois. 



The region in the vicinity of Urbana, where the greater 

 part of these records have been made, is an elevated prairie, 

 without marshes or swamps ; the streams are mere ditches ; 

 and the natural timber is but a thin woodland tract skirting 

 one of these ditches and a nearby artificial pond. The most 

 complete data are from a cemetery adjacent to the campus; 

 an artificial forest of about 18 acres and over 40 years old 

 which is on the campus ; and a few rapidly disappearing 

 hedges and brushy patches in the outskirts of the city. More 

 extensive streams and woodlands twelve to twenty miles dis- 

 tant, have been visited very frequently but not daily and hence 

 the data from them have not been used in this discussion. 



^ Contribution from the Zoological Laboratory, University of Illi- 

 nois, No. 87. 



