EASTERN VESPER SPARROW 877 



"At about 4:20 p.m. on July 13, 1956, in a field one mile west of 

 Mount Pleasant, Mich., Frank Gardner and I flushed a vesper spar- 

 row from its nest at the base of a small mullein plant. The bird 

 feigned injury, fluttered along the ground, and disappeared in the 

 vegetation about 20 feet from the nest. After checking the nest, 

 which contained two eggs, we left the area, but returned at 4:50 

 p.m., again flushing the bird from the nest. Again it fluttered away. 

 We then \\-ithdrew to a small weed-covered mound 60 feet from the 

 nest and, while hiding somewhat in the weeds, watched the nest with 

 8-power binoculars. At 4:52 p.m. we realized that a 13-lined ground 

 squirrel {Citellus tridecemlineatus) had quickly approached the nest 

 and had taken one of the eggs. The ground squirrel sat on its haunches 

 about 4 inches from the nest, holding the egg in its forepaws, and 

 rolled the egg over and over as it ate the contents. After a few min- 

 utes, the squirrel dropped the apparently empty shell and took up a 

 crouched position over the nest, as if eating the other egg. At 4:57 

 p.m. a vesper sparrow appeared and instantly pounced upon the gi'ound 

 squirrel and pecked it from above as it dashed away into some grass. 

 The sparrow immediately returned to the nest, hesitated a moment to 

 eat the shell, which the ground squirrel had discarded, and then set- 

 tled on the nest. At 5:03 p.m. the ground squirrel again approached 

 ■within a foot of the nest and the sparrow left the nest, attacked the 

 squirrel, and drove it into the grass. The sparrow returned, stood by 

 the nest for a moment, then departed. We went to the nest and found 

 it empty; only a small fragment of an egg sheU lay on the ground 

 beside the nest." 



F. N. Hamerstrom, Jr., and F. Hamerstrom (1951) report finding 

 the remains of vesper sparrows at nests of the Cooper's hawk. 



Reports in the literature on cowbird parasitism of vesper sparrow 

 nests are conflicting. H. Friedmann (1929) considered the species "a 

 common victim," but added that there was just one record from Ithaca, 

 N.Y. E. H. Eaton (1914) considered the vesper sparrow among the 

 "commonest" of hosts in New York State. Francis C. Evans found 

 only one out of 85 nests parasitized at the Edwin S. George Reserve 

 in southern Michigan, and G. M. Sutton found no parasitism of 11 

 June and July nests at the Reserve, although he saw a vesper spar- 

 row feeding a fledgling cowbird, July 25, 1936. In southwestern 

 Michigan, James F. Ponshair found four nests parasitized out of a 

 total of 25 nests; in Ohio, M. B. Trautman found 3 of 14 nests para- 

 sitized. 



The available evidence suggests that the degree of parasitism of 

 vesper sparrow nests varies both with the nesting habitat and with 

 the time of the breeding season. Because relatively few species are 

 nesting at the start of the cowbird's laying season, April and early 



