are
no longer than a few feet between adjacent shrubs and trees, but
occasional sustained flights are as long as 300 feet. The birds fly as
low as 2 feet above ground, but have often been observed as high as 70
feet above the ground.

In courtship and protracted territorial disputes, where chase between
sexual partners or a pair of antagonists occurs, looping flights are
observed. The wings are beaten as the birds climb and many aerial
maneuvers are performed in the course of the glide.

_Foraging and Food Habits_

The Bell Vireo has been characterized as a thicket forager (Hamilton,
1958:311; Pitelka and Koestner, 1942:104), but in my experience it is
not restricted to low level strata; birds forage from ground level
upward, both in thickets and isolated trees ranging in height from 3
feet to 65 feet. The tendency to forage at higher levels is in part
dictated by the presence of tall trees within the various territories.

Territories 1 through 7 (1960) contained from three to ten trees
surpassing 40 feet in height. They grew singly or in small groves. The
Bell Vireos foraged fully 20 per cent of the time in these trees. Food
was sought throughout the leaf canopy.

Behavior in foraging in larger trees followed a routine pattern.
Typically a pair alighted in a tree at a height of 15 feet. Then the
female hopped to a perch a foot above the one upon which she landed.
The male succeeded her to the perch she had previously occupied. The
pair in effect spiraled around some large, essentially upright,
branch, in foraging. The birds usually reached higher perches in this
manner rather than by flying upward 10 to 15 feet to them. This manner
of progression within a tree is reminiscent of a similar habit of the
_Cyanocitta_ jays. Presumably, the habit of the Bell Vireo of foraging
in higher strata is facilitated by the absence of other species of
arboreal foraging vireos.

Chapin (1925:25) found the Bell Vireo to be more insectivorous in its
food habits than any other North American vireo. He found 99.3 per
cent of all food contained in 52 stomachs to be of animal origin. Only
three times have I seen a Bell Vireo take food of vegetable origin. On
September 9, 10, and 14, 1959, I noted a male eating wild cherries
over a period of 65 minutes of observation. Chapin (1925:27) noted
that beginning in July vegetable matter represented 1.57 per cent of
the bird's subsistence, and thereafter slightly more until fall
migration.