24 THE AUDUBON BULLE Tae 
MORE BOOK REVIEWS 
HOST RELATIONS OF THE PARASITIC COWBIRDS, by Herbert Fried- 
mann. Bull. United States Nat. Mus. No. 233: 276 pp. 1963. $1.25. 
The present monograph brings up to date and summarizes the in- 
formation accumulated on cowbird parasitism since 1929. Complete, an- 
natated accounts of the Brown-headed and Bronzed Cowbirds, followed 
by discussions and tabular accounts of hosts of the South American Shiny, 
Screaming, and Giant Cowbirds, are contained in this informative mono- 
graph. 
The three species and subspecies of Brown-headed Cowbirds, Molothrus 
ater, are known to have parasitized 206 species (333 species and subspecies) 
of birds. The Eastern form, Molothrus ater ater, is known to have parasitized 
138 species, of which no less than 47 are cited for Illinois. 
In frequency of host selection, 50 hosts “account for approximately 
7,800 records out of a total of about 9,000 instances of cowbird parasitism.” 
Dr. Friedmann states: “It would seem that the proportionate role they 
play in nature is, if anything, even greater than these figures would sug- 
gest, since many instances of parasitism upon common hosts are left un- 
recorded because of their repetitive nature, while most cases involving 
uncommon victims are published as records of particular interest.” The 
Yellow Warbler; Song Sparrow; Red-eyed Vireo; Chipping Sparrow; 
Eastern Phoebe; Rufous-sided Towhee; Ovenbird; Yellowthroat; American 
Redstart; Indigo Bunting; Yellow-breasted Chat; Red-winged Blackbird; 
Kentucky Warbler; Traill’s Flycatcher; Bell’s and Yellow-throated Vireo, 
and Field Sparrow are the 17 species most frequently parasitized. , 
Frequency of parasitism of common hosts is approximately 60 percen‘ 
containing a single cowbird egg, while 2 and 3 eggs are less frequent 
Extremes run as high as 9 cowbird eggs reported from a nest of a Wooc 
Thrush, while 11 cowbird eggs have been reported (Berger, 1955) from < 
six-storied nest of the Yellow Warbler. | 
Dr. Friedmann states: “The number of parasitic eggs that may be 
accepted by a host ordinarily appears to be limited to not more than it) 
own maximum clutch number. In the case of many of the smaller hosts 
however, such a number of cowbird eggs would overcrowd the nest to thi 
point of physical discomfort to the covering bird and might lead to deser: 
tion? { 
Other interesting topics include: breeding success of host and parasite 
hatching potential of host species; mutual effect of parasite and host on eg. 
production; duration of parasite interest in host nests; interspecific preen 
ing invitational behavior; foster parent-offspring relationship; and reactio 
of host to parasitism. 
Of the 206 species known to have been parasitized, 101 species, ¢ 
slightly less than half, are known to have reared young of the parasit 
Additional studies along this line will undoubtedly increase this numbe 
Dr. Friedmann has done an outstanding job in revising his earlier wor 
on parasitism. This excellent publication should be on the bookshelf of a 
animal behaviorists and ornithologists. 
Harlan D. Walley, 717 North Elm St., Sandwich, Hline. 
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