122 U.S. NATIONAL MUSEUM BULLETIN 233 



Here we have a body of evidence clearly at odds with data from 

 elsewhere in the range of the host. No matter how satisfying it might 

 be to have a mathematical evaluation of the host-parasite relation- 

 ship, it is meaningless to consider adding these two bodies of evidence 

 to produce an "average" behavioral response. Such an average would 

 have no biological significance since it would reflect the picture in no 

 one individual. The only justifiable approach is to admit that there 

 is a surprising variability of response on the part of the chat and 

 that, in terms of present data, this variability appears to be local. 

 Whether this evidence should be taken to imply, or even to suggest, 

 the existence of parasite-tolerant and parasite-intolerant "strains" 

 within the species cannot be debated without more detailed data from 

 many parts of its range; such data should include the inheritance, if 

 any, of parasite-tolerance in the area where it is known to occur. 



In 1924 in the lower Kio Grande Valley of Texas, I found the 

 western race of the chat to be a common host of the dwarf race of 

 the cowbird. Of four nests which were found, all were parasitized. 

 Hanna (1928, p. 161) recorded five parasitized nests in southern Cali- 

 fornia. E. M. Tait informed me many years ago that he found three 

 nests with cowbird eggs (artemisiae) at Trout Creek Point, British 

 Columbia. Mr. Guy Love wrote to me of a similar nest which was 

 found on June 22, 1908, in Decatur County, Kansas. The instance 

 involved the eastern race of the parasite and the western race of the 

 host — the first time this particular subspecific combination has been 

 found. 



Hooded Warbler 



Wilsonia citrina (Boddaert) 



Although the number of definite instances of parasitism has increased 

 in recent years, the hooded warbler may be described as a somewhat 

 uncommonly recorded victim of the brown -headed cowbird. Thirty- 

 two cases have been noted, distributed among the following states: 

 Connecticut, New York, New Jersey, Pennsylvania, Maryland, Vir- 

 ginia, Georgia, Alabama, Indiana, Illinois, and Michigan. Stewart 

 and Robbins (1958, p. 329) mention five cases in Maryland. Five, 

 possibly six, occm-rences have been reported from one locality. Lake 

 Orion, in Michigan: Middleton (1952, p. 7) gave four records; 

 Wallace and Black (1949, p. 15) found a hooded warbler feeding 

 two of its own and one cowbird fledgling; and Wickstrom (1951, 

 p. 114) noted a record of a parasitized nest which may be among 

 the four listed by Middleton. On the basis of these and other recent 

 records, it seems that increasing data may make it necessary to recon- 

 sider the status of the hooded warbler with respect to the cowbird. 

 The best that may be said at present is that, while this warbler is not 

 a frequently imposed upon species, it cannot be called a very uncom- 



