rst bird arrived at the study tract about May 5. No
additional birds were heard singing until the third week of the month,
in which eight new males were noted. As mentioned, in 1960 field work
was begun in mid-April and the study area was traversed daily. No
birds were detected until late afternoon of May 3, when one,
presumably a male, was seen foraging.

Lawrence (1953:50) has reported that males of the Red-eyed Vireo
precede females in the breeding area by as much as two weeks; the male
Red-eyed Vireo forages but sings little in the pre-nesting period. The
male Bell Vireo arrives first at the breeding area but precedes the
female by only a few days. On the morning of May 4 the first male was
singing from a number of perches while ranging over an area of seven
acres. This area encompassed territories later occupied by three
pairs, 2 (1960), 4 (1960), and 5 (1960). Late on the afternoon of May
4 the first courtship songs were heard and the first male was seen
with a mate at 6:20 p.m. Eight additional males arrived from May 6
through May 18. A tenth male was discovered in the vicinity of
territory 9 (1960) on June 18, 1960.

[Illustration: FIG. 2. Seasonal movement as indicated by the
curve for spring arrival (A), based on the earliest dates for
27 years, and the curve for autumn departure (B), based on the
latest dates for 21 years in northeastern Kansas.]

_Fall Departure_

The average date of departure for 21 years in northeastern Kansas is
September 3 (fig. 2-B). The earliest date is August 14 from Concordia,
Cloud County, Kansas (Porter, unpublished field notes). The latest
date is September 27 (Bent, 1950:262) from Onaga, Pottawatomie County,
Kansas. In 1959 the last vireo was seen at the study tract on
September 14. The birds do not all depart at the same time. On
September 1 there were still five singing males in the study area; by
September 10 there were three and on September 13, only one.

GENERAL BEHAVIOR

_Flight_

In "straight-away" flight the Bell Vireo undulates slightly. In a
typical flight several rapid, but shallow, wing beats precede a
fixed-wing glide of from 1 to 15 feet in length. Because the wings are
extended horizontally during the glide, the bird does not move
distinctly above or below the plane of flight. The White-eyed Vireo
generally appears to be slower and more lethargic in flight than the
Bell Vireo. In the breeding season most flights of the Bell Vireo