dueling | Combat | disputes
-------------+-----------+---------+--------+-----------------
Prenesting | 3 | 3 | 2 | 6 min. 40 sec.
Building | 8 | 8 | 6 | 3 min. 8 sec.
Incubation | 1[B] | 1 | ... | 20 min.
+-----------+---------+--------+-----------------
Totals | 12 | 12 | 8 | 5 min. 30 sec.
-------------+-----------+---------+--------+-----------------

[B] Directed against a stuffed Bell Vireo.

Probably as a direct result of these conflicts, a neutral zone
approximately 300 feet wide developed between the two territories. By
May 14 this intervening area was occupied by male 4 (1960). By this
date both 1 (1960) and 2 (1960) were involved in nestbuilding and 4
(1960) was not challenged for several days.

Maximum tail-fanning prior to attack also appears as an element of
aggressive behavior in White-eyed Vireos. A brief skirmish between a
male of this species and a small, greenish passerine was observed at
the Natural History Reservation on May 25, 1960. The White-eyed Vireo
was singing from a perch 30 feet high in a dead elm, when the
unidentified passerine landed 10 feet distant. The white-eye ceased
regular song and uttered several catbirdlike calls, and at the same
time slightly depressed and fully fanned the tail. After 10 seconds,
the white-eye lunged at the intruder, striking it in mid-air. A brief
looping flight ensued through the branches of the elm before the
intruder was able effectively to retreat.

_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 CONFLIC