Chipping Sparrow

Spizella passerina (Bechstein)

At the time of the 1963 compendium (Friedmann, p. 162) but a single instance was known of parasitism on the subspecies S. passerina arizonae by the dwarf cowbird M. ater obscurus. A second case may be added, a set of 4 eggs of the sparrow and 1 of the parasite, taken in San Luis Obispo County, California, 28 April 1939, now in the Santa Barbara Museum of Natural History.

The collections of the Western Foundation contain 267 sets of eggs of the chipping sparrow, only 8 of which (3.0 percent) are parasitized. This is to some extent a reflection of the bias against sets with cowbird eggs of some of the early collectors whose materials are now incorporated in the Western Foundation, and may also suggest a geographical difference in the incidence of parasitism on this sparrow in the west as compared with the east. We may recall (Friedmann, 1963:162) that in Ohio, Hicks had found that 60 out of 115 nests examined (over 50 percent) were parasitized, and that in southern Quebec, Terrill had found cowbird eggs or young in 16 out of 138 nests (11.6 percent). One of us (S.I.R.) studied 83 nests in Cheboygan and Emmet counties, Michigan, in 1968 and 1969, and found that 30 (36.2 percent) of them were parasitized. Of 155 nests found in Manitoba, Saskatchewan, and Alberta, reported to the Prairie Nest Cards files at the Manitoba Museum, 20 (12.9 percent) were parasitized. Of 733 nests in Ontario reported to the files at Toronto, 216 (29.5 percent) were parasitized. On the other side of the picture is the experience in Pennsylvania of Harrison (1975:244) who found cowbird eggs in only 2 out of 29 nests examined, a very low incidence of 6.9 percent.

CLAY-COLORED SPARROW