RIO GRANDE VIREO 241 



range extends into the United States only in the Kio Grande Valley 

 of Texas, mainly in Cameron and Hidalgo Counties. It is the 

 smallest of the races of the white-eyed vireos, similar to our northern 

 bird, but duller colored and with a paler wash of yellow on the flanks. 



We found the Eio Grande vireo common around Brownsville, Tex., 

 and discovered two nests, one on May 24 and one on May 25, 1923. 

 The first was 5 feet from the ground, suspended from a lower branch 

 of an ebony tree near the town ; it was a pretty nest, new but deserted ; 

 so I took it, but it blew out of the car and was lost. On the following 

 day, while hunting through the dense thickets along a resaca, we 

 found the second nest, 3 feet up in a small bush, containing four 

 heavily incubated eggs; the eggs could not be saved, but the nest is 

 now before me. Externally it measures 2i/2 inches in diameter by 

 about the same in height; the internal diameter at the top is about 1% 

 by 1% inches, and the depth of the cup is about 2 inches; the rim 

 is somewhat incurved and is verj^ firmly attached to the supporting 

 twigs, being securely bound with spider webs and woolly substances; 

 the walls of the nest are not thick, but they are very firmly woven, 

 with dead leaves, a few green leaves, many pieces of paper from wasp 

 or hornet nests, strips of thin inner bark, lichens and spider nests, all 

 reinforced with fine grass fibers and securely bound together with 

 spider silk ; the lining is of very fine grasses and white hairs ; a few 

 rootlets and bits of wool have been worked into the body of the nest. 



Dr. Herbert Friedmann (1925) also found the Rio Grande vireo 

 common around Brownsville, of which he says : "This Vireo sings and 

 acts just like the typical form in the northern states. Its nest is harder 

 to find than most Vireos' because of the density of the foliage of the 

 places in which it nests and also because the nests are placed towards 

 the inside of the mesquite clumps instead of on out-hanging branches 

 as are the nests of the Red-eyed Vireo. According to Camp this bird 

 is very commonly parasitized by the Dwarf Cowbird. Only four nests 

 were found, of which two were empty and the other two had three eggs 

 each." 



There are four nests of the Rio Grande vireo, containing from three 

 to five eggs each, in the Thayer collection in Cambridge, all collected 

 by, or for, F. B. Armstrong in Tamaulipas, Mexico, between April 2 

 and 11. They are mostly like my nest, as described above, but one 

 ver}^ pretty nest is made largely of lichens and mosses held in place 

 by some very fine twigs and bound with the usual amount of spiders' 

 silk. The nests were placed 3 to 6 feet above the ground. The largest 

 nest measures about 3 inches in diameter and about the same in height 

 externally. 



The eggs are characteristic of the species. Tlie measurements of 30 

 eggs average 18.0 by 13.6 millimeters; the eggs showing the four ex- 

 tremes measure 19.1 by 13.7, 18.3 by 14.2, and 16.6 by 13.2 millimeters. 



