A STUDY OF A RED-EYED VIREO'S NEST 

 WHICH CONTAINED A COWBIRD'S EGG 



By T. C. Stephens 

 The nest of the Red-eyed Vireo {Vireo olivacea) upon which 

 this study was made was found on June 21, 1916, and contained 

 on this date two Vireo eggs and one Cowbird's egg. The nest 

 was of the usual type, and was suspended in a very low-hanging 

 branch of a red elm tree ( Ulmus fulva, fig. 1 ) . The general loca- 

 tion was the rather heavily wooded lake shore back of Gull Point, 

 on West Lake Okoboji, Iowa. 



The position of the nest was so low as to be ideal for study, 

 but the distance from the Laboratory militated against attempt- 

 ing a continuous study. It was planned, however, to make a 

 few short studies, especially to watch the behavior of the young 

 Cowbird. Accordingly two full days from daylight till dark, 

 and one-half day from daylight to noon, were devoted to this 

 work. On July 8 the study began at 4:45 a. m., and continued 

 without intermission until 8 :22 p. m. On J uly 9 the observa- 

 tions began at 5:00 a. m. and continued till 12:00 m. On July 

 10 in the afternoon a brief visit was made to the nest and a single 

 feeding visit was recorded, No. 176. On July 11 observation 

 again started at 5 :05 a. m. and continued until 8 :00 p. m. Ob- 

 servations for shorter periods were made on the 13th, 14th and 

 17th. 



The work at the nest-side during these periods was shared by 

 the writer and Mr. Arthur F. Smith about equally; the latter, 

 however, taking the early morning hours. The writer here ex- 

 presses his obligation to Mr. Smith for this cordial cooperation. 



To distinguish the young birds they were marked mth aniline 

 dyes in alcoholic solution. On July 8 the nest contained the 

 Cowbird and two young Vireos. One of the latter was marked 

 with methelyn blue, and designated ''Blue;'' the other was left 

 unmarked, and designated ''White." 



The two parents were distinguished as follows : The male was 

 much more shy and approached the nest more cautiously, and 



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