198 U.S. NATIONAL MUSEUM BULLETIN 233 



northeastern Argentina, and they have generously sent me data from 

 their unpubUshed work. 



When one considers the vast geographic range of the shiny cow- 

 bird — from Patagonia to the Colombian-Panamanian border and 

 to some of the islands of the West Indies — and when one also considers 

 the very large number of available host species in all of that diversified 

 area, it is obvious that the known instances of host choice by the 

 shiny cowbird are still little more than a sampling of what one may 

 expect to be reported in time. A slight inlding of this may be gathered 

 from Mrs. Mitchell's experience in Brazil (1957, pp. 204-205), where 

 she recorded seeing a female shiny cowbird attempting unsuccess- 

 fully to enter the nest of a becard, Platypsaris rufus, and of a fly- 

 catcher, Satrapa icterophrys, both of which probably will be found 

 eventually to be victimized there; as yet this fact has not been re- 

 corded. And these are the relatively casual observations of one 

 observer in a limited area! It is true that in some parts of South 

 America, such as most of Argentina (except the extreme north), 

 Uruguay, and southeastern Brazil, we probably now know the vic- 

 tims most frequently imposed upon by the parasite. On the other 

 hand, there are many species of birds that seem to be utilized rather 

 seldom but only because, so far, merely a few records have been noted 

 by occasional observers. South American birds have yet to be ade- 

 quately studied by sufficient numbers of observers. 



The earlier reports in this series have become exceedingly 

 difficult for readers to use and compare because of numerous changes 

 in nomenclature and systematic treatment of the various species and 

 subspecies involved. In a few cases, what had been recorded as 

 separate forms now have been united; others have been divided in 

 ways that are different from earlier usage. To give a composite pic- 

 ture of the present state of knowledge, I am including in tabular form a 

 list of all the known hosts, divided into races both of the host and of the 

 parasite. In this table no columns have been made for two races 

 of the shmy cowbird, nigricans and riparius, for the reason that 

 so far no host records are available for them. A perusal of this 

 table shows that the host list for Molothrus honariensis now includes 

 193 species and subspecies (148 species) of birds, as compared with 

 98 forms (82 species) in my 1929 list. 



