THE COWBIRDS. 



597 



find an abundauce of food at that time of tlie year, and tlie return 

 migration to their winter liomes begins usually in the latter half of 



October. 



The eggshell of the Cowbird is compact, granulated, moderately 

 glossy, and relatively much stronger than in the eggs of its near 

 allies the Icteridce. The ground color varies from an almost pure 

 white to grayisli white, and less often to pale bluish or milky white, 

 and this is usually profusely covered over its entire surface with specks 

 and blotches varying in color from chocolate to claret brown, tawny 

 and cinnamon-rufous. In an occasional specimen the markings are 

 confluent and the ground color is almost entirely hidden by them; in 

 the majority, however, it is distinctly visible. These markings are 

 usually heaviest about the larger end of the egg, and in rare .nstances 

 they form an irregular wreath. The eggs vary greatly in shape, 

 ranging from ovate to short, rounded, and elongate-ovate, the first 



predominating. o xr +• 



The average measurement of 127 specimens in the U. S. :Nationai 

 Museum collection is 21.45 by 16.42 millimeters, or 0.84 by 0.65 inch; 

 the largest egg measures 25.40 by 16.76 millimeters, or 1 by 0.06 inch; 

 the smallest 18.03 by 15.49 millimeters, or 0.71 by 0.61 inch. 



MOLOTHRUS ATER OBSCURUS (Gmelin). Dwarf Cowbird. 



Sturnus ohscurus, Gmelin, Systema Naturii-, i, ii, 1788, 804. 



Mloloihrm^ ater rar. ohscurus, CouES, Birds of- the Northwest, 1874, 180, in text 

 (B — C 211a, R258a, C 314, U 495 a). 

 Similar to preceding, only smaller. Length (male), about 7-7.50; 

 wing, 3.70-4.15 (3.93); tail, 2.85-3(2.91); culmen, 0.57-0.63 (0.60); tar- 

 sus, 0.93-1 (0.96) ; female smaller. 



Geographical range.— Mexico and adjoining portions of the United 

 States from southern Texas to southwestern Arizona and Lower Cali- 

 fornia. 1 O J- • 



The breeding range of the Dwarf Cowbird in the United States is 

 coincident with its geographical distribution. It can only be considered 

 as a summer resident, although a few appear to winter in southern 

 Arizona, as I shot an adult male on Rillito Creek, near Tucson, on 

 January 24, 1873. It usually arrives from its winter home in southern 

 Mexico about the middle of March, and is then found associating with 

 different species of Blackbirds, especially Brewer's Blackbird, and fre- 

 quenting the vicinity of cattle ranches, roads, and cultivated fields. 

 By April 15 the flocks have scattered, and small parties of from 5 to 12 

 may now be seen in suitable localities, such as the shrubbery along 

 water courses, springs, etc., where other small birds are abundant. 

 The character of its food and its general habits as well, are similar to 

 those of the common Cowbird, which it closely resembles, being only a 

 trifle smaller. In middle Texas the two races intergrade to some extent, 

 and It is claimed both breed there. In the lower Kio Grande valley, 



