1204 U.S. NATIONAL MUSEUM BULLETIN 23 7 part 2 



these, two nests held one and two cowbird eggs respectively but no 

 clay-colored eggs. Both nests were abandoned. Three nests con- 

 taining both clay-colored and cowbird eggs were abandoned; 5 nests 

 successfully fledged one cowbird each, both alone and in company 

 with fledging clay-colors; one nest vacated three cowbirds. From 

 28 eggs, eight cowbirds were fledged, or a reproductive efficiency of 

 28.5 percent. One nest had a cowbird egg imbedded in the lining; 

 in another, two of the four pallida nestlings were removed simul- 

 taneously, presumably by a cowbird, and one cowbird egg was sub- 

 stituted. Only 6 of the 20 parasitized nests contained the full com- 

 plement of four clay-colored eggs, suggesting the removal of one or 

 more pallida eggs by the cowbird. The latest egg-laying date for the 

 cowbird was July 4." 



W. R. Salt (1966) states: "in two cases after a cowbird's visit, eggs 

 of the Clay-colored Sparrow were found just outside the lip of the 

 nest but held by the surrounding grasses." 



A. H. Shortt (MS.) states that the cowbu'd was the most persistent 

 enemy of clay-colored sparrows at Deer Lodge, Manitoba, in 1932- 

 1933. Of 50 nests he studied 26 were parasitized; 13 were deserted 

 after being parasitized. From 31 cowbird eggs, eight young were 

 reared (none in the same nest with young clay-colors) , or a reproduc- 

 tive efficiency of only 25.8 percent. The sparrows seemed more 

 tolerant of parasitism toward the close of the nesting season, for 

 reproductive efficiencies of cowbirds were 10.5 percent during the 

 first nesting of the clay-color; 50.0 percent dui'ing the second nesting. 

 Young cowbirds left the nest on the 10th day. 



L. H. Walkinshaw (1944a) found no cowbird eggs in 40 nests near 

 Lo veils, Mich. 



Six recently fledged juveniles that G. C. Kuyava banded at Duluth 

 in July and August 1958, were each host to from one to three small 

 green adult hippoboscid flies, Ornithomyia fringillina. Kuyava also 

 noted many unidentified parasite eggs on the underside of one bird's 

 wing. Near Duluth in June 1950, P. B. Hofslund found several 

 insect larvae in the nostrils of a soHtary but very active nesthng. 

 G. Robert Coatney and EvaHne West (1938) report that the only 

 clay-colored sparrow examined in the Lincoln, Nebr., region was 

 negative for blood-inhabiting organisms. While migrating, adults 

 may suffer casualties from TV towers (H. B. Tordoff and R. M. 

 Mengel, 1956). 



Fall. — After nesting is finished, clay-colored sparrows move about 

 in small, loose flocks in shrubbery, fields, gardens, and among trees, 

 uttering a constant tsip much like that of the field sparrow. When 

 flushed they tend to fly low instead of high. Southbound migrants 

 arrive in Texas between August 3 (El Paso) and November 18 (Tar- 



