HOST RELATIONS OF PARASITIC COWBIRDS 207 



five nests found in 1958, all were parasitized; of three found in the 

 same area in 1957, one or two were similarly affected. The high 

 incidence of parasitism on this species, taken in consideration with 

 the number of other, unmolested, but apparently suitable, potential 

 hosts in the unmediate area, suggests pronounced preference on the 

 part of the parasites for this wren. The record refers to the nominate 

 race of the host. 



South American House Wren 

 Troglodytes musculus Naumann 



One additional subspecies of the wren, T.m. tobagensis, has been 

 found to be parasitized by the shiny cowbird (subspecies M.b. mini- 

 mus). In Tobago, at Caledonia, on October 29, Mees (Junge and 

 Mees, 1958, p. 127) twice saw a fledgling cowbird being fed by adidts 

 of this species. A second record for the Chilean race of the Avren 

 {T.m. chilensis) recently has been reported — a nest with 4 eggs of the 

 wren and 3 of the cowbird (subspecies M.b. bonariensis) found at 

 Vucro de Linares in November, 1948, by R. Barros Valenzuela 

 (1956, p. 91). The eggs of the wren had been punctured, apparently 

 by the coM'-bird. 



In Peru, the subspecies T.m. audax was known as a host of the 

 shiny cowbird (subspecies M.6. occidentalis) only on the basis of 

 Taczanowsld's statement (1884, pp. 422-424) that it had been re- 

 ported as such by Stolzmann and Jelski. Recently, Dr. Maria 

 Koepcke has informed me that near Lima she has seen a recently 

 fledged cowbird attended by a pair of house wrens. Howe and 

 Singh (1960, pp. 94, 95) considered this wren (subspecies clarus) as 

 the favorite and, indeed, the only recorded host in British Guiana, as 

 did Harper (1907, p. 66) years earlier. Similarly Haverschmidt 

 (1955, p. 127) concluded that this bird was the principal host in 

 Surinam; he informed me (in litt.) of 11 instances that had come 

 under his own observation there. In Trinidad, Herklots (1961, p. 

 222) reported frequent impositions on this wren; he wrote that several 

 nests had been found each with from 1 to 3 eggs of the shiny cowbird. 



The frequent choice of this host by the parasite in northeastern 

 South America is noteworthy in view of the fact that in Ai-gentina, 

 Paraguay, and Uruguay Troglodytes musculus is victimized much less 

 commonly. Even in these more temperate southern latitudes, how- 

 ever, this wren is parasitized more frequently than its counterpart. 

 Troglodytes aedon, is parasitized anywhere in North America by the 

 brown-headed cowbird. 



Long-tailed Mockingbird 



Mirnus longicaudatus Tschudi 



The subspecies albogriseus of this species of mockingbird has been 

 added to the Hst of victims of the shiny cowbird (subspecies Al.b. 



