ADDITIONAL DATA ON THE 



HOST RELATIONS OF THE 



PARASITIC COWBIRDS 



By 

 HERBERT FRIEDMANN 



Director, Los Angeles 

 County Museum of Natural History 



Publication of my 1963 book (see bibliography) on this subject 

 prompted a number of observers to send me their records of the two 

 North American species of cowbirds, the brown-headed and the 

 bronzed, with the request that I bring out a supplement to it. To this 

 data I have added a few recently published records to make the present 

 paper as useful as possible. In all cases the reader should consult my 

 1963 book for full data. 



Brown-Headed Cowbird 



Molothrus ater 



The hosts of this wide-ranging cowbird now include two new 

 species, one of which, the spotted sandpiper, can only be looked upon 

 as an "accidental" victim. (Occasional additions to the list of ill- 

 adapted hosts do occur but are without biological significance. They 

 mean only that a cowbird with an egg to be laid may lay it in an 

 unsuitable nest if a suitable one is not available.) A real, but by no 

 means new, problem is raised by new data on Bell's vireo and the 

 cardinal as cowbird hosts : how to treat quantitatively with statistical 

 significance rapidly and unevenly changing total blocks of record data 

 while maintaining a relative appraisal among the frequently victimized 

 fosterers. No workable solution to this difficult question has yet been 

 found. 



For many years I have been trying to interest biometricians in the 

 problem of estimating the quantitative aspects of the host-parasite 

 relationship in many of the frequent fosterers, but the number of 

 variables has discouraged the few who even began to survey the prob- 

 lem. Scott's recent data on the cardinal, discussed below, has caused, 



SMITHSONIAN MISCELLANEOUS COLLECTIONS, VOL. 149, NO. 11 



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