HOST RELATIONS OF PARASITIC COWBIRDS 97 



in Hudspeth County, Texas, on June 8, 1958. R. S. Crossin (in litt.) 

 informed me that on May 24, 1959, along San Pedro River, St. David, 

 Cochise County, Arizona, he collected a set of 2 eggs of Lucy's warbler 

 along with 1 of the dwarf cowbird. In the collections of the Santa 

 Barbara Museum of Natural History there are two more parasitized 

 sets of eggs, which were taken in 1917 near Tucson, Arizona; three 

 similar sets formerly were in that museum. 



Parula Warbler 



Parula americana (Linnaeus) 



The parula warbler seldom has been reported to be molested by 

 the brown-headed cowbird. While this may be due in part to the 

 observer's difficulty in finding the dainty, pensile nests of the host 

 within the drooping masses of Spanish moss it prefers as a breeding 

 site, the total number of the warbler's nests which have been found 

 is large enough to indicate the low percentage of cowbird parasitism. 

 It follows that neither the warbler nor the cowbird are important 

 in the economy of the other. Altogether, only 12 records have been 

 noted, distributed among the following states: Massachusetts, 

 Connecticut, New York, New Jersey, Pennsylvania, Maryland, 

 Virginia, Indiana, Alabama, Oklahoma, and Texas. The eastern 

 race of the parasite, M. a. ater, is involved in aU the records except 

 for one instance: a parasitized nest collected by H. P. Attwater in 

 Kerr County, Texas, in 1895, and now in the U.S. National Museum; 

 in this case, it is the dwarf race, M. a. ohscurus, which is involved. 

 Many years ago, the late J. P. Norris informed me that he had an 

 unusually large "set" of eggs taken in Northampton County, Vir- 

 ginia, May 27, 1890, by G. B. Benners, comprising 3 eggs of the 

 warbler and 3 of the brown-headed cowbird. 



Yellow Warbler 

 Dendroica petechia (Linnaeus) 



The yeUow warbler has been known for a long time as one of the 

 most frequently imposed upon cowbird victims. The actual records 

 which have been observed must be well over a thousand. I stopped 

 accumulating them after I had noted more than 900 instances. All 

 three races of the brown-headed cowbird and five races of the yellow 

 warbler — aestiva, amnicola, rubiginosa, morcomi, and sonorana — 

 are involved. The great mass of records come from practically 

 every province of Canada and every state of the United States 

 where the warbler and the cowbird both occur as breeding bhds. 



In recent years, studies of the yellow warbler have yielded important 

 quantitative data on the relations between it and the cowbird. 

 Hicks (1934, pp. 385-386), in Ohio, found 62 out of 146 nests to be 



