74 U.S. NATIONAL MUSEUM BULLETIN 233 



change. Green, at Des Moines, Iowa, wrote (1887, p. 91) that one- 

 half of the nests of this thi'ush which were found contained 1 or more 

 cowbird eggs and that, in a single nest, he had discovered as many as 

 6 of the parasitic eggs with 2 of the thrush's. Similarly, Keyes and 

 Williams (1888, p. 48) recorded the observation that this thrush 

 frequently was parasitized, with from 1 to 4 cowbird eggs per nest. 

 Stoner, also in Iowa (1919, pp. 80-81), recorded 12 parasitized nests 

 of this bird. Since 1929, the total number of records of parasitism 

 has increased by 50 percent, but so has the number of Iowa records. 

 R. F. Johnston (in litt.) informed me that 6 out of 28 nests which he 

 found in Kansas were parasitized. 



In Minnesota, Hofslund (1950) noted 14 parasitized nests, one of 

 which contained the surprismg number of 9 cowbird eggs in addition 

 to 2 of the thrush. He noted two different wood thrushes, each 

 feeding three fledgling cowbirds. 



A stdl more astonishing record is that of a nest found in the Rondeau 

 Provincial Park, Ontario, in 1960, by Garry Hanes, and reported to 

 me by R. D. Ussher; the nest contained 1 egg of the thrush and no 

 less than 12 of the cowbird. Walter Nickell informed me that the 

 area had been sprayed with DDT, a fact which may have reduced the 

 number of nesting biixls and may have forced the cowbirds to "con- 

 centrate" on fewer nests. In repl}'' to my queries, Mr. Ussher wrote 

 me that the eggs were of four distinct types: 3 were rather narrow 

 and pointed with very heavy specklings; 2 were large eggs, coarsely 

 speckled with heavily blotched wreaths at the large end ; 4 were lightly 

 and uniformly speclded; and 3 were rather coarsely but uniformly 

 speckled. The appearance of the eggs suggested that four hen 

 cowbirds may have been involved. 



The late Lynds Jones informed me many years ago that he laiew of 

 a case wherein a wood thrush threw a cowbird's egg out of its nest, 

 just as the robin does regularly. This remains only an exceptional 

 instance because the thrush usually accepts the parasitic egg; in fact, 

 Langille (1892, pp. 162-164) even found a wood thrush sitting in a 

 nest containing a solitary cowbu'd egg. 



Simmons (1915, p. 329) found a parasitized nest six miles west of 

 Houston, Texas, April 9, 1911. This is the only recorded instance of 

 the dwarf cowbird parasitizing the wood thi'ush. 



Hermit Thrush 



Hylocichla guttata (Pallas) 



Four races of the hermit thrush (guttata, auduboni, faxoni, and 

 polionota) have been reported as hosts of two races of the brown- 

 headed cowbird (ater and artemisiae) . As far as published information 

 indicates, the species is rather uncommonly imposed upon, but it 



