Aggressive Behavior of the Female
The female Bell Vireo is concerned primarily with the defense of the nest and the young and she rarely assists the male in defense of distant parts of the territory. She employs the same threat displays as the male.
Interspecific Relationships
A number of meetings between Bell Vireos and other species were observed in the course of the study (Table 4). Resident pairs of this species exhibited different degrees of tolerance toward other species. Many birds, including Cardinals, Field Sparrows, Painted Buntings and Mourning Doves were ignored completely. Chickadees evoked responses characterized by slight increase in song and some anxiety; this was perhaps owing to similarity in size, motion and call notes. Warblers, when met with, were invariably chased. They may be momentarily mistaken for rival vireos.
Table 4. Interspecific Conflict Observed in 1959 and 1960.
| Species | Number of conflicts | Phase of breeding cycle | Behavior of Bell Vireos | |||
|---|---|---|---|---|---|---|
| HFT[C] | S | TF | A | |||
| Coccyzus americanus | 1 | Nestling period | x | |||
| Cyanocitta cristata | 3[D] | Nestling and incubation period | x | x | x | x |
| Parus atricapillus | 1 | Prenesting | x | |||
| Molothrus ater | 1 | Nestling period | x | x | ||
| Dendroica petechia | 1 | Prenesting | x | x | ||
| Geothlypis trichas | 1 | Nestbuilding | x | x | ||
| Pituophis catenifer[E] | 1 | Post-fledging | x | x | ||
[C] HFT = head-forward threat; S = scolding; TF = tail-fanning; A = attack.
[D] Includes attack against a dummy Blue Jay.
[E] The Bull Snake is here included because the vireos directed typical aggressive displays towards it.