House Wren

Troglodytes aedon Vieillot

Miller (1963:47) found this wren to be a host of the shiny cowbird at San Antonio, western Andes, Colombia. The local race of the wren is T. aedon striatulus, which has not otherwise been reported as a cowbird victim. Dr. J. I. Borero and Father Antonio Olivares have informed us of numerous observations they have made of parasitism on the house wren in the region of Cali, Colombia, as well. Previously seven other subspecies, T. a. albicans, T. a. tobagensis, T. a. musculus, T. a. rex, T. a. audax, T. a. chilensis, and T. a. bonariae, had been known to be parasitized. The present record refers to the cowbird race M. bonariensis cabanisii, a subspecies not hitherto reported as including this wren among its victims.

From Trinidad there were earlier (Friedmann, 1963:207) a number of records of parasitism on this wren (race T. aedon albicans, of which T. a. clarus is a synonym). To these may be added 17 more such instances, demonstrating beyond question that the house wren, in spite of its small size, is the most frequently reported host of the shiny cowbird in that island that has many potential (and actual) hosts. Of these additional cases, 10 have come to us through the kindness of Dr. D. W. Snow, and the other 7 were reported to us by R. P. ffrench. In 1 of the latter's instances there were 4 eggs of the wren and 9 of the cowbird, a nest that could hardly have been successful. In 9 of the 10 cases observed by Snow, the parasite's eggs were accepted and incubated and the young cowbirds were reared; in only a single case were the “eggs thrown out after cowbird visit.”

From the combined evidence supplied by ffrench and Snow, it becomes apparent that the cowbird parasitizes other hosts in localities where the house wren is absent, but that the parasite prefers the wren when it is available. (See the note on Agelaius icterocephalus in the present paper).

The house wren has also been found, by Paul Schwartz, to be a victim of the shiny cowbird (race M. bonariensis venezuelensis) in the vicinity of Caracas, Venezuela.

This wren is of more than usual interest, since in Argentina and Uruguay it is seldom imposed upon (by M. bonariensis bonariensis) while in Guyana and Trinidad it is a favorite host choice of M. bonariensis minimus (Friedmann, 1963:207). By way of contrast, it may be mentioned that in North America the house wren is extremely infrequently parasitized; thus in Ontario, only 1 out of 709 nests reported was parasitized by M. ater.

PATAGONIAN MOCKINGBIRD

Mimus patagonicus (Lafresnaye and d'Orbigny)

A fourth instance of parasitism on this mockingbird is a set of 2 eggs of the host and 1 of the parasite, collected at Maquinehao, Rio Negro, Argentina, 26 October 1911, by J. R. Pemberton, now in the collections of the Western Foundation. A fifth instance was found near Patagones, Buenos Aires Province, 15 December 1972, by S. Narosky.

CHILEAN MOCKINGBIRD