T OBSERVED IN 1959 AND 1960.

==================================================================
| Number | Phase of | Behavior of
| | | Bell Vireos
Species | of | breeding +------+---+----+---
|conflicts| cycle |HFT[C]| S | TF | A
---------------------+---------+--------------+------+---+----+---
_Coccyzus | 1 | Nestling | | | |
americanus_ | | period | -- | x | |
| | | | | |
_Cyanocitta | 3[D] | Nestling and | | | |
cristata_ | | 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.

Blue Jays were vigorously attacked, especially late in incubation and
throughout the nestling period of the Bell Vireo. I did not see a jay
struck, but a vireo would circle one closely as it perched and pursue
it when it flew, following as far as 100 yards beyond territorial
bounds. The buzz, ZZ-ZZ-ZZ-ZZ, was uttered in conjunction with this
harassment.

A stuffed jay placed eight feet from a nest elicited threat display
and displacement behavior from the owners of the nest, but no attack.
Incuba