HOST RELATIONS OF PARASITIC COWBIRDS 39 



regularly and, at times, rears multiple young of the parasite. As an 

 example of an extremely successful host, we might mention the song 

 sparrow, of which species Salmon (1933, p. 100) recorded an instance 

 wherein three j^oung cowbirds were reared, and Lees (1939, p. 121) 

 reported a case wherein no less than five young cowbirds were seen 

 attended by a pair of these sparrows. 



In the list given below I have attempted to evaluate the various 

 species on the basis of the actual records of theii" having raised young 

 cowbirds. This has resulted in some cases in a rather deceptive 

 definiteness, which merits explanation at this point. In compiling 

 the data for this list, I have often come across published statements 

 to the effect merely that a given species was parasitized, without 

 any further details. These I have concluded were probably egg 

 records and I have not used them here. In addition, the absence 

 from this list of some species which are included in the total host 

 catalog may be due to the fact that many of the actual published 

 data were contributed by egg collectors, who took the eggs they found, 

 rather than let them hatch; or the absence may be due to the fact 

 that the data were reported by passing observers who did not have 

 the time, opportunity, or interest to revisit the nests to learn the 

 eventual outcome of each, 



A consequence of this, reflected in the comments given after each 

 species, has been to present as equally valid quantitative estimates 

 the data from casual observations with the results from much fuller 

 knowledge in other species. In order to show the scope of the infor- 

 mation from which I have deduced the degree to which each host 

 has been a success for the parasite, I have added, where it seemed 

 desk-able, the total number of records of cowbird parasitism known 

 to me. In such cases, the accounts of the individual species in the 

 catalog may be consulted for fm-ther details. 



mourning dove : one instance (with an black-capped chickadee : once (out of 



element of doubt) 4 records of parasitism) 



eastern kingbird: once (out of 15 brown creeper: one instance (only 



records of parasitism) record of parasitism) 



scissor-tailed flycatcher: once (out of a wrentit: once (out of 4 records of 



very few records of parasitism) parasitism) 



eastern Phoebe: frequently 1^°"^^ ^'^^n: three times (out of 6 



Acadian flycatcher: several times ^ ^^^,.^ , ,_ r ■, 



_, .„, „ , , , ,. Carolina wren: once (out of a dozen 



Iraill s flycatcher: several times j r -i.- \ 



or so records of parasitism) 



western flycatcher: twice (out of 6 eatbird: twice (out of 22 records of 



records of parasitism) parasitism) 



eastern wood pewee: frequently i^j-q^.^ thrasher: several times 



tree swallow: at least once (out of a ^ood thrush: several times 



small number of records of para- hermit thrush: twice (out of about 



sitism) 20 records of parasitism) 



630590—63 4 



