6 U.S. NATIONAL MUSEUM BULLETIN 233 



1929 list (1931, 1934, 1938, 1943, 1949), it has become exceedingly 

 difficult to present the data for the use of the reader who does not 

 have the time or facilities to correlate the various records. This is 

 due largely to the many changes in nomenclature that have been 

 introduced into the literature. Two completely revised editions 

 (1931 and 1957) of the official check-list of North American birds 

 have been published by the American Ornithologists' Union since 

 my first catalog. Many additional races of birds have been recog- 

 nized, a fact which has necessitated critical reallocations of many 

 hundreds of the older records, and in some instances forms that were 

 previously considered species are now united as conspecific races. 

 In the present catalog I have adhered strictly to the last (fifth) 

 edition of the check-list and have not included any deviations from 

 it no matter how justifiable they may have seemed. Over the years 

 many students have written me about birds they were studying, as 

 they found it difficult to put together the pertinent cowbird data for 

 these particular host species. This has been especially the case with 

 individuals contributing life history accounts to the series of Bent 

 volmnes, and this continuing source of inquiries, together with other 

 queries, as I stated in the preface, has led me to think that a need 

 existed for the present catalog. 



In the annotated catalog of hosts of the brown-headed cowbird 

 the species is taken as a unit and is discussed as such, although 

 reference is made to the race or races involved in each case. To 

 make the total mass of records immediately available to investigators 

 interested in a particular race of either the host or the parasite, a 

 complete tabular summary precedes the catalog. Inasmuch as 

 the racial differentiations of the various host species occur along 

 many different geographic patterns, frequently quite dissimilar to 

 that of the parasite, it follows that a single race of a given species 

 of victim may be imposed upon by more than one race of the parasite, 

 and also that several races of a species of host may be parasitized 

 by the same race of the cowbird. The tabulation (pp. 41-44) reveals 

 that the eastern race, ater, of the cowbird is known to have parasitized 

 138 species (174 species and subspecies) of birds; the northwestern 

 race, artemisiae, to have affected 101 species (139 species and sub- 

 species) of birds, and the small southwestern race, obscurus, to have 

 victimized 86 species (122 species and subspecies) of birds. The 

 total for the brown-headed coAvbird, as a species, is 206 species (333 

 species and subspecies) of victims. 



Frequency of Host Selection 



Of the total number of birds included in the present catalog, 

 more than half are uncommon, rare, or even accidental victims. No 



