66 U.S. NATIONAL MUSEUM BULLETIN 233 



me that he once found this bird victimized at Santa Paula on June 13, 

 1917, when he collected a set of 1 egg of the victim and 1 of 

 the parasite. These eggs later went to the collection of the late 

 J. Hooper Bowles. In the collections of the Western Foundation of 

 Vertebrate Zoology there is another set: 4 eggs of the wren tit and 1 of 

 the dwarf cowbird, taken at Santa Paula on May 8, 1936. Kowley 

 (1930, p. 131) put on record a similar instance of cowbird parasitism 

 in the San Gabriel River district, May 8, 1927, with a nest containing 

 3 eggs of the wrentit and 1 of the cowbird. Mr. N. K. Carpenter 

 wrote to me of still another instance. In a record from Inverness, 

 Marin County, Williams (1957, p. 428) reported that on July 22 one 

 of these wrentits was seen attending and feeding a recently fledged 

 cowbird. This last record refers to the race rwfula of the host. 



House Wren 



Troglodytes aedon Vieillot 



The house wren is parasitized very infrequently, partly because of 

 its habit of nesting in holes and partly because of its pugnacious 

 nature, which may be a deterrent to visiting cowbirds. An unex- 

 plained mystery, however, is involved here: the South American 

 house wren, T. musculus, with essentially similar habits, is imposed 

 upon far more often by the shiny cowbird, Molothrus bonariensis. 



Only six actual instances, distributed from Ontario, New York, 

 Michigan, and Iowa, to North Dakota and Alberta, have come to 

 my attention, A few authors, such as Bendire and Davies, have 

 included the house wren in their lists of cowbird victims, but without 

 any supporting data. The cases known to me are as follows. Kells 

 (1885, p. 106) found the race haldwini of the wren to be parasitized 

 near Listowel, Ontario, in 1884. Alfred Eastgate informed me many 

 years ago that he once found an egg of the cowbird (subspecies 

 artemisiae) in a nest of the western race of the wren ( T. a. parkmanii) 

 in North Dakota. Later, T. E. Randall sent me a second record for 

 the western house wren, involving a nest with 5 eggs of the wren and 

 1 of the cowbird taken at Boyle, Alberta, June 10, 1934. Finally, on 

 July 12, 1947, James Hodges saw a pair of western house wrens feeding 

 a recently fledged brown-headed cowbird at Duck Creek, Scott County, 

 Iowa. In this instance I deduce, on geographic grounds, that the 

 parasite must have been of the nominate race, M.a. ater. Hamerstrom 

 (1947) noted a house wren feeding a recently fledged cowbird in 

 Michigan. In this case there was some question as to whether or not 

 the young cowbird came from an earlier brood, as at the time the 

 only pau* of wrens present had a nest with eggs. The cowbird might 

 have been reared by some other species, and, as a result, the observa- 

 tion involved only its begging from and being fed by a wren. 



