nests. Sun-shading has been noted in other species
where the nest was poorly protected from the sun. Lawrence (1953:62)
observed this behavior at two Red-eyed Vireo nests in conifers. The
"sun-shield" posture of the Bell Vireo does not correspond to any of
the sunning postures described by Hauser (1957).

_Feeding of the Nestlings_

Both sexes fed the young, and presumably began shortly after the first
nestling hatched. My data indicate that the female does more feeding
than the male (Table 10); in about eight hours of observation a total
of 67 morsels were brought, 43 by the female and 24 by the male, for
an average of once every 7.6 minutes. Nice (1929:17), however,
observed a male to bring food 53 times as compared to 21 visits by the
female. In five and one-half hours of watching, meals were brought
once every 4.9 minutes. Du Bois (_in_ Bent, 1950:257) recorded seven
trips in an hour and forty minutes, or one every fourteen minutes.

At three nests containing young the adults were sometimes silent and
sometimes vocal on their approach. The female often emitted a subdued
_chee_ which, coupled with the vibration of the nest caused by her
arrival, elicited begging behavior from the young. None of the males
was heard to utter such a call, but I have the impression that they
often did call although I failed to hear the sounds. The males did, on
occasion, sing several songs as they approached, even with food held
in their beaks. Such singing elicited begging from the nestlings. Once
the eyes of the young were open they often began begging when a silent
adult was within two or three feet of the nest; begging behavior
probably is elicited by tactile, auditory or visual stimuli in that
order, or, as the nestling period proceeds, by any combination of
these stimuli.

TABLE 10. FEEDING OF THE NESTLINGS.

====================================================
Day of | Length of | Adult involved
nestling period | observation +---------+---------
| | Male | Female
-----------------+--------------+---------+---------
1 | 30 min. | 3 | 5
2 | 60 min. | 1 | 4
3 | 60 min. | 2 | 5
4 | 30 min. | 1 | 4
7 | 60 min. | 4 | 7
2 | 60 min. | 3 | 3
6 | 60 min. | 3 | 6