BELL’S VIREO STUDIES 
289 
side to side, so stonelike was its posture. Each of these sitting 
periods would last from ten to twenty minutes. Although other 
nesting birds occasionally have been seen to sit at the nest edge, 
they have seldom been known to sit for such long periods or with 
such regularity on the part of both male and female as with 
• Fig. 45.— This- shows the adult as she appears in the nest. She is hardly 
noticeable and while an intruder is nearby she never makes a sudden move 
with her head lest the act attract attention. Both male and female take 
turns at incubating. (Nest number 10.) 
tlie Bell’s Yireo. The reason for this habit could not be ascer- 
tained. 
SINGING FROM THE NEST. 
While out on field trips the writer has frequently noticed 
that by going to a place where he has heard a Bell’s Vireo sing- 
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