BELL’S VIREO STUDIES 
291 
the discovery of this habit. Nest number 6 was the object of 
investigation and on June 22, 1910, the writer observed the 
bird singing from the nest. Whether or not this vireo practices 
it as a general thing has not yet been worked out, but the fact 
that the writer has in an unusual number of cases found the 
Fig. 47. — The young Cowbird in this nest was fed many a large cater- 
pillar but the two vireo’s eggs failed to hatch. (Nest number 10.) 
nest where the bird had been singing, would seem to be pretty 
strong circumstantial evidence of a more or less general habit. 
A POSSIBLE DECREASE IN NUMBERS. 
In this clay of bird conservation little effort seems to have 
been made so far to ascertain whether the Bell's Vireo is in- 
