No eggshells were found in nests on the days of hatching. Presumably they had been removed by the parents. Nolan (1960:234) indicates immediate disposition of the eggshell after hatching. Lawrence (1953:62) suggests that conspicuous removal of eggshells by the female Red-eyed Vireo informs the male that the young have hatched.
Both sexes brood and the exchange of partners resembles that described for the incubation period. Decrease in brooding in the daytime begins about the sixth day of nestling life. Nolan (1960:235) reports a sharp decrease in brooding when the oldest nestlings are seven days old. Brooding decreases notably on the sixth day of nestling life in the Red-eyed Vireo (Lawrence, 1953:62). Nice (1929:17), Hensley (1950:244), and Nolan (1960:235) report that the female Bell Vireo assumes a slightly greater role in brooding than the male.
Apparent sun-shading was noted at nest 3-b (1959) at 2:00 p.m. on June 17, 1959, on the fifth day of the nestling period. The nest contained three young. An adult flew to the nest; while standing on its rim the bird dipped its head into the nest six times, afterward appeared to be eating a fecal sac, than shifted position to the unattached portion of the rim, gaped three times, thereupon spread its wings, and sat motionless 35 minutes. In this attitude it formed an effective shield sheltering the young from direct sunlight penetrating the thin foliage of the honey locust in which the nest was situated. The temperature at this time was 95° F., but the sky was partly cloudy. By 2:30 p.m. the sky had become overcast and the sun passed behind a cloud. Although sunlight no longer fell directly upon the nest, the bird remained in the shielding posture for another five minutes before flying from its perch. Sun-shading was not observed at either of the other nests containing young; dense overhead vegetation protected those 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 nestling period | Length of observation | Adult involved | |
|---|---|---|---|
| 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 |
| 7 | 30 min. | 3 | 3 |
| 9 | 60 min. | 4 | 6 |
| Totals | 510 min. | 24 | 43 |
Not all trips made by parents resulted in successful feeding of young; some visits seemed to be purely for inspecting the young. On other occasions the adults experienced difficulty in transferring food to the young, and, thus thwarted, would themselves eat the food. Nice (1929:17) estimated that from five to twelve of a total of seventy-five meals were eaten by adults.