184 IT.S. NATIONAL MUSEUM BULLETIN 237 pabt i 



Stevenson and Meitzen (1946) report that a dickcissel was brought 

 to the nest of a Sennett's white-tailed hawk. 



A certain number of dickcissels are casualties of the highways. 

 Starrett (1938) found four killed by automobiles in central Illinois, 

 and Smith (1938) reports one killed in flight by a passing car at 

 Sydney, Nova Scotia. Tuck found a dickcissel that had been run 

 over by a railway train near Terra Nova, Newfoundland. James 

 Hodges (1950) reports that a dickcissel was caught in small interlaced 

 wires of an electric line and starved to death. 



A nest I found in central Illinois July 2, 1918, in a thick cluster of 

 grapevines 5 feet above the ground had become so badly infested with 

 mites that the young were almost killed. I found the same mites, 

 less abundant, in a number of nests. Nathan Banks of the Museum 

 of Comparative Zoology identified them as a new species of Liponysus, 

 allied to the common poultry mite. 



Perhaps the greatest foe of the dickcissel, especially those that nest 

 in clover and alfalfa fields, is the mowing machine. Cutting the first 

 crop destroys the early nests, and the late or second nest are often 

 victims of a second harvest. In one 20-acre field near Atwood, 111., 

 I found four nests, three with eggs and one with young that a mowing 

 machine had destroyed. Spurrell (1921) notes frequent destruction 

 of nests in Iowa by the cutting of clover fields. He found many 

 eggs while loading hay. Destruction by mowers may be serious 

 enough to affect materially local dickcissel populations. 



Fall. — The fall migration of the dickcissel has been given less 

 attention than the more spectacular spring arrival. It is, neverthe- 

 less, quite as interesting. In August at the close of the nesting season, 

 the dickcissels rove about for a short time as family groups. These 

 soon unite with others, which in turn may join stUl larger aggregations 

 to form roosts of several hundred individuals. In 1908 a roost that 

 contained considerably more than 300 birds on August 20 had very 

 few on September 1, and was deserted by September 10. A roost I 

 watched the summer of 1918 occupied the banks of a large drainage 

 ditch whose sides, for a distance of nearly a mUe, were covered with 

 giant ragweeds and horseweeds 8 to 10 feet high. Although the 

 season was excessively hot and dry, the ditch contained refreshingly 

 cool water. This and the admirable concealment the tall weeds 

 provided made it an ideal concentration center for many dickcissels. 

 A few could be seen feeding on the weed seeds or bathing in the ditch 

 almost every hour of the day, but the mass of individuals came in 

 between sunset and dark. On August 5 it sheltered only about 50 

 birds and on August 8 about 125. On August 10 I counted 485 adults 

 and young, and doubtless more than twice that number were concealed 

 by the dense growth. By August 15 a marked diminution in the 



