454 U. S. NATIONAL MUSEUM BULLETIN 211 



Desert Song Sparrows, Black-throated Sparrow, and Vermilion Fly- 

 catcher following in the order named." 



Usually only one egg of this cowbird is laid in the nest of the host, 

 but often two are laid and sometimes more. In the W. C. Hanna 

 collection is a set of two eggs of the orchard oriole with four of the 

 cowbird, and a set of the Arizona hooded oriole, containing four 

 eggs of the dwarf cowbird and one of the bronzed cowbird. 



W. L. Dawson (1923) tells of a pair of least vireos that "showed 

 notable valor in driving off from time to time a snooping female 

 who spied upon their progress. Rousing one morning to a sudden out- 

 cry, I arrived upon the scene in time to see an irate Vireo drag a 

 Cowbird from the nest and hold her for a dramatic moment suspended 

 in mid-air — until the Vireo's strength gave out and both fell struggling 

 to the ground. But in spite of this instant and summary punishment, 

 the Cowbird had accomplished her mission." 



Wilson C. Hanna writes to me that he has a set of eggs of the 

 California black-chinned sparrow that contains an egg of the dwarf 

 cowbird, and a set of the black-throated gray warbler with one egg 

 of this cowbird; each nest held two eggs of the host and one of the 

 parasite; both sets were taken in San Bernardino County, Calif. 



Eggs. — Bendire (1895) says: "In general appearance and shape 

 the eggs of the Dwarf Cowbird resemble those of the preceding species 

 [eastern species], and the same description will answer for both; but 

 they appear on an average to be somewhat less heavily spotted, which 

 gives them a lighter appearance, and they are also considerably 

 smaller. 



"The average measurement of thirty-seven specimens in the United 

 States National Museum collection is 19.30 by 14.99 millimetres, or 

 0.76 by 0.59 inch. The largest egg in this series measures 20.57 by 

 15.49 millimetres, or 0.81 by 0.61 inch; the smallest, 18.03 by 13.74 

 millimetres, or 0.71 by 0.54 inch." 



Young. — It has been stated that the young cowbird does not push 

 its nest mates out of the nest, as the European cuckoo does, but Daw- 

 son (1923) says: "I once found a nest which contained only a lusty 

 Cowbird, while three proper fledglings clung to the shrubbery below, 

 and one lay dead upon the ground." 



Behavior. — Dawson (1923) describes a habit, common to all the 

 races of the species, as follows: "In feeding upon the ground about 

 corrfds the Cowbirds are quickly actuated by the flock impulse, rising 

 as one bird at a fancied alarm. After alighting upon a fence or upon 

 the unprotesting backs of cattle, they hop down again one by one as 

 confidence becomes established. They greet each other always with 

 quivering bodies and uplifted tails, and that upon the most trivial 

 occasions." 



