424 U. S. NATIONAL MUSEUM BULLETIN" 211 



tendency to repeat the experiment would soon disappear by cross- 

 breeding with individuals of normal breeding habits, unless the 

 habit proved to be beneficial to the species, and no such proof is 

 evident. We frequently find fresh eggs of robins and other birds 

 laid on the ground, but failure to reach their nests has never de- 

 veloped parasitic habits in these birds. 



The North American cowbirds have been split into three recog- 

 nized races; two other races have been described, but have not been 

 admitted to the A. 0. U. Check-List. 



The eastern cowbird, the subject of this sketch, breeds in eastern 

 North America from southern Ontario, southern Quebec, Nova Scotia, 

 and New Brunswick south to central Virginia, southeastern Ken- 

 tucky, central Tennessee, south central Arkansas, Louisiana and 

 central Texas, and west to Minnesota, northeastern Iowa, south- 

 easter Nebraska, southwestern Kansas and New Mexico. 



It may breed, or at least lay eggs, casually farther south in the 

 Atlantic States. In this connection, the reader is referred to an 

 interesting paper by Thomas D. Burleigh (1936) suggesting that 

 the cowbird may lay eggs during migration, of which he gives some 

 evidence. This may account for some of the southern breeding 

 records. 



Spring. — The eastern cowbird has not far to go on its spring 

 migration. It is one of the earlier migrants, leaving its winter range 

 in the Southern States during March and reaching the northern 

 parts of its breeding range during the first 2 weeks in April, or some- 

 times before the end of March. 



According to Friedmann (1929): 



The Cowbird migrates by day, early in the morning and late in the afternoon. 

 I know of no data tending to show that this species indulges in nocturnal migra- 

 tion, but it may do so to some extent. * * * The Cowbird commonly migrates 

 with the Red-winged and Rusty Blackbirds and the Grackles; in fact these three 

 are usually found together. Other less common associates are Meadowlarks 

 and Robins in the east, and Brewer's and Yellow-headed Blackbirds in the west. 



Doubtless many Cowbirds succumb annually to the perils attendant upon 

 migration but so far as I have been able to find there are no definite records of 

 such happenings. Because they migrate chiefly by day no Cowbirds have been 

 picked up dead around lighthouses or the bases of tall monuments and buildings." 

 Bendire (1895), however, tells of one that was blown out to sea and came aboard 

 a vessel, "fully 1,000 miles east of Newfoundland." 



During his studies of the cowbird at Ithaca, N. Y., Friedmann 

 (1929) divided the spring migration into six more or less separate 

 phases, much like similar phases in the migration of the red-winged 

 blackbird. The first to appear were the vagrants, at dates ranging 

 from March 1, 1919, to March 14, 1922; these were wandering in- 

 dividuals coming before the true migration, consisting mostly of 



