olan hardly qualify as
flight song, for this term implies use of a distinctive vocalization
not uttered in other circumstances.

_Daily Frequency of Song_

In the morning, Bell Vireos usually began singing a few minutes before
sunrise. Their songs were invariably preceded in the study area by
those of Western Kingbirds, Robins, Mourning Doves, Mockingbirds,
Cardinals and Meadow Larks. Bell Vireos sang relatively little after
6:30 p.m., even on the longest days of the year. The latest daytime
singing that was recorded was seven songs at 7:18 p.m. on June 20,
1960. A Cardinal in the vicinity sang for a full hour after this.

_Types of Vocalizations_

Six vocalizations were readily distinguishable in the field. These are
divisible into songs and call notes.

1. Primary song. It has been described by Pitelka and Koestner
(1942:103) as an "irregular series of harsh and sharp, but slurred
notes preceded by a few distinct notes of the same quality and ending
with a decided ascending or descending note of similar harshness." The
terminal note may also be somewhat abbreviated and intermediate
between an ascending or descending note. The song is sometimes
delivered as a couplet that consists of a phrase ending on a
descending note. This delivery is typical of incubation and later
renesting. During early season activities, the bird utters a phrase
ending on the descending note as many as 15 times before a phrase
ending on an ascending note is heard.

A sonagram of a single phrase, one of several recorded on May 9, 1960
(the third day of building of nest 1-b 1960), consists of 10 notes,
the first of which is distinct. The remaining notes are slurred. This
phrase is 1.4 seconds in length.

Songs are delivered most rapidly in the course of territorial disputes
and defense. The song is loudest in times of nestbuilding and periods
of aggressive behavior. At these times, on clear, calm days, the songs
are audible 100 yards away. Singing in the nestling period and
post-breeding season is audible at distances of no more than 50 feet;
such notes have been termed "whisper songs." Table 1 summarizes
singing rates at different periods of the nesting cycle in several
situations and under various weather conditions.

Songs are of equal frequency in the immediate vicinity of the nest and
elsewhere in the territory. Nice (1929:17) also found this to be true.
Perches can be almost at ground level or as high as 60 feet. Forty per
cen