164 U.S. NATIONAL MUSEUM BULLETIN 233 



and New Mexico. No new information has been acquired since my 

 first (1929, p. 223) account, which may be summarized as follows. 



Jensen (1923, p. 4G1) wrote that he had found cowbird eggs in 

 nests of this sparrow in northern Santa Fe County, New Mexico, 

 but he gave no details. What may be one of Jensen's records is a 

 parasitized clutch of eggs, taken on June 7, 1919, and now in the 

 collections of the Western Foundation of Vertebrate Zoology. In 

 the files of the U.S. Fish and Wildlife Service there is a field note by 

 Merritt Gary from the Upper Green River Valley of W^yoming; the 

 note reports a recently fledged cowbird attended and fed by Brewer's 

 sparrow at Gora, Wyoming, on August 8. Another field note, by 

 H. E. Anthony from the same area and with the same date, probably is 

 based on the identical case. 



The records refer to the typical race of the sparrow, to the north- 

 western race, artemisiae, of the cowbird in Wyoming, and to the 

 nominate race, ater, in New Mexico. 



Field Sparrow 



Spizella pusilla (Wilson) 



The field sparrow is a frequent victim of the brown-headed cowbu'd. 

 Over 125 records have been noted, distributed from Quebec in Ganada 

 to the following of the United States: Gonnecticut, Illinois, Indiana, 

 Iowa, Kansas, Maryland, Massachusetts, Michigan, Missouri, New 

 Jersey, New York, Ohio, Oklahoma, Pennsylvania, Rhode Island, 

 South Dakota, Tennessee, Virginia, and Wisconsin. 



Almost all of the records refer to the typical, eastern race of the 

 field sparrow. The lack of additional data for the western race, 

 arenacea, probably reflects a lack of human observation rather than 

 an actual difference in the lives of the sparrow and the cowbird in 

 that area from western Oklahoma to the Dakotas and Montana. 



In Ohio, Hicks (1934) found 159 nests of this sparrow, of which 51 

 contained eggs or young of the cowbird — a notably high percentage 

 of parasitism. In Iowa, Anderson (1907, pp. 297-300) considered the 

 field sparrow one of the two most parasitized birds; a similar con- 

 clusion was made in Ohio by Dawson (1903, p. 15). 



A recent study by Walkinshaw (1949) in Galhoun Gounty, Michi- 

 gan, has given new insight into the host-parasite relations of the field 

 sparrow and the brown-headed cowbird. Eggs of the latter (appar- 

 ently from one individual!) were laid in 20 field sparrow nests, of 

 which 15 were deserted when the parasite laid its own and removed 

 a host egg. At least 17 field sparrow eggs and four young disappeared 

 from 16 nests, presumably removed by the cowbird. It follows from 

 this that, at times and in places such as Galhoun Gounty, the cowbird 

 may be a very serious factor in the welfare of the field sparrow. How- 



