786 U.S. NATIONAL MUSEUM BULLETIN 237 part 2 



Sutton reported singing peaks at sunrise and early evening, but Hyde 

 found singing lessened toward evening. 



W. E. Saunders (MS.) reports that Henslow's sparrows sang inter- 

 mittently throughout the night of July 20-21, 1935, at Morpeth, 

 Ontario, and that not more than 15 minutes elapsed without a song 

 being heard. Other observers have had similar experiences. The 

 species has also been observed singing incessantly when rain was pour- 

 ing down. Perhaps lessened light intensity stimulates singing, and 

 in this respect the bird seems crepuscular. 



Behavior. — This small sparrow spends much of its time concealed in 

 the grass and dense vegetation in which it lives. During the breeding 

 season it does not move far from its nest, which is often hard to locate 

 because it is so well concealed and because the female usually runs 

 some distance from it before flushing, and returns to it on foot as well. 

 When not singing, it is seldom noticed unless it is flushed from the 

 cover. It is difficult to flush, for it apparently places great reliance 

 on its marvelously concealing coloration, and either runs through the 

 grass from the intruder or remains motionless in hiding until almost 

 stepped upon. When it does flush, it seldom flies more than a few 

 yards before dropping back into the vegetation. It evidently has a 

 strong game effluvium, as bird dogs often point it, to the annoyance 

 of their quail-hunting masters. 



Sutton (1928a) describes its flight as being more erratic and un- 

 dulating than that of the grasshopper sparrow. The wmg beat usually 

 alters just after the bird takes flight, and the tail and rump are twisted 

 in a peculiar and characteristic manner. 



Field marks. — The Henslow's is confused mainly with the grass- 

 hopper and Le Conte's sparrows, which frequently share its habitat, 

 particularly in winter. The best field marks are its distinctly reddish 

 wings and the olive-green nape (rufous-brown in the Le Conte's). 

 The Henslow's streaked breast and flanks distinguish it from the clear- 

 breasted adult grasshopper sparrow. 



Enemies. — Although nests of Henslow's sparrow are occasionally 

 victimized by the brown-headed cowbird, the species appears to escape 

 heavy parasitism, possibly because the nests are so well hidden. No 

 data are available on the percentage of nests parasitized (which is 

 apparently low), or as to whether the presence of a cowbird nestling 

 precludes successful fledging of the young Henslow's sparrows in the 

 nest. J. T. Southard writes me of finding nests of this species con- 

 taining two cowbird eggs in addition to three or four host eggs. 



Snakes are probably the foremost predators of the species. In Penn- 

 sylvania, Henslow's sparrows and their eggs were found to constitute 

 12 percent of the diet of specimens of the blue racer {Coluber constrictor) 

 examined by Ruthven et al. (1928). Hawks also prey on this sparrow. 



