250 BULLETIN 17 0, UNITED STATES NATIONAL MUSEUM 



its perfection in only the eastern races ; some of the western races show 

 an occasional brownish phase; and an intermediate, brownish phase 

 occurs rarely in the eastern races. Many years ago E. M. Hasbro uck 

 (1893) made an extensive study of this subject, and published a paper 

 based on the data obtained from 3,600 birds. He attempts to — 



show, first, that while the red, the gray and the intermediate phases are at present 

 but individual variations of the same species — the gray was the ancestral stock; 

 second, that the gray bird evolved the red, which at some future time will be a 

 recognized sub-species with a range peculiar to itself, and thus dichromatism is 

 one step in the evolution of the Screech Owl, while the various phases exhibited 

 are the transitorial stages of development of one species from another; third, that 

 this condition of affairs is influenced by four powerful factors (two of which tem- 

 perature and humidity, are dominant powers in geographic distribution), the 

 most potent of which is temperature; fourth, that the predominating distribution 

 of the respective colors is largely confined to the faunal divisions of the Eastern 

 United States, and as such is approaching the sub-specific differentiation of the 

 two phases. 



His five maps illustrate the ranges of the eastern races, the areas 

 occupied by each one of the phases exclusively and those in which one 

 of the phases predominates, and the distribution of the phases in com- 

 parison with temperature, humidity, and forest growths ; the distribu- 

 tion of the phases seems to correlate fairly well with the distribution 

 of these factors. He makes the statement that whereas the offspring 

 of parents of two different phases, or of two red parents, may be all 

 red, all gray, or of both colors, "not a single record can be found of the 

 offspring of a pair of gray birds showing the slightest trace of red." 

 This statement seems remarkable, but I have no evidence to the 

 contrary. 



Food. — The screech owl enjoys a varied bill of fare including almost 

 every class of animal life. Dr. A. K. Fisher (1893b) summarizes its 

 food as follows: "Of 255 stomachs examined, 1 contained poultry 

 [pigeon]; 38, other birds; 91, mice; 11, other mammals; 2, lizards; 

 4, batrachians; 1, fish; 100, insects; 5, spiders; 9, crawfish; 7, miscel- 

 laneous; 2, scorpions; 2, earthworms; and 43 were empty. " He says 

 of their hunting methods: "At night-fall they begin their rounds, 

 inspecting the vicinity of farm-houses, barns, and corncribs, making 

 trips through the orchard and nurseries, gliding silently across the 

 meadows or encircling the stacks of grain in search of mice and 

 insects. Thousands upon thousands of mice of different kinds thus 

 fall victims to their industry." 



Dr. Paul L. Errington (1932c) says: "My Wisconsin record for 

 Screech Owl vertebrate and large invertebrate prey totals up to 137 

 individuals, in the following proportions: Norway rat, 1; meadow 

 mouse, 49; deer mouse, 37; shrew (Blarina, 6; Sorex, 1), 7; small bird 

 (predominantly English Sparrow according to feather evidence of 

 kills), 36; fish, 4; crayfish, 3." 



