458 U. S. NATIONAL MUSEUM BULLETIN 211 



Early date of fall arrival: Sonora — Rancho La Arizona, August 18. 

 Late date of fall departure: Arizona — Tucson, September 22. 

 Egg dates. — Arizona: 9 records, May 30 to July 7; 4 records, 

 June 12 to June 28. 



Texas: 44 records, April 1 to July 5; 22 records, May 12 to June 8. 



TANGAVIUS AENEUS AENEUS (Wagler) 



Red-Eyed Bronzed Cowbird 

 HABITS 



The red-eyed cowbird is the best known and most widely distributed 

 of the bronze-backed cowbirds. Its breeding range extends from 

 eastern Texas (San Antonio) southward along the eastern coast 

 region of Mexico and Central America as far as Panama. It differs 

 from the type race of northwestern Mexico in having the back and 

 rump entirely bronze color, thus lacking the violaceous rump of 

 typical aeneus. The common names are not helpful in distinguishing 

 our two subspecies, for both have red eyes and both have bronze backs. 



Alexander F. Skutch contributes the following account of the 

 distribution and haunts of this species in Central America: 



"In northern Central America the red-eyed cowbird is found from 

 the lowlands of both coasts far up into the mountains, breeding in the 

 highlands of western Guatemala at least as high as 8,500 feet above 

 sea-level. In southern Central America it is less widely distributed. 

 In Costa Rica it appears to be absent from the heavily forested 

 Caribbean lowlands and from the almost equally heavily forested 

 lowlands on the Pacific side of the country, to the southward of the 

 Gulf of Nicoya; but it is present in the drier lowlands around and 

 to the north of the Gulf of Nicoya (Guanacaste), the central highlands, 

 and the upper portions of the Caribbean slope. It avoids the forest, 

 and its local distribution is largely determined by the presence of open 

 country. Hence it is more abundant in the highlands, where there is 

 a dense human population, with many open fields and pastures, 

 than in the less populous and more uniformly forested lowlands. 

 For the same reason, it is more common in the dry and relatively 

 open Pacific lowlands, and in arid, mountain-rimmed valleys in the 

 Caribbean drainage, than in the heavily wooded coastal districts 

 of the Caribbean; yet in Guatemala and Honduras it has invaded 

 these districts where they have been extensively cleared for banana 

 plantations and pastures. Red-eyed cowbirds often fly in compact 

 flocks over some of the larger highland cities of Central America, and 

 I have seen many of them in the central plaza of San Jos6, Costa Rica. 



"Red-eyed cowbirds perform at least short migrations, largely 



