dae, the behavior of
the Red-eyed Vireo (_Vireo olivaceus_) is best documented (Sutton,
1949; Lawrence, 1953; Southern, 1958). With this species authors have
concentrated on the mechanics of the breeding season and their reports
contain little discussion of the aggressive and epigamic behavior of
the bird.

The amount of information on the ritualized behavior of the Bell Vireo
and related species heretofore has been meager. I observed breeding
behavior from its inception in early May through the summer of 1960.
It is hoped the resulting information will serve as a basis of
comparison in future studies of behavior of vireos; such ethological
data are becoming increasingly important, especially as an aid in
systematics.

ACKNOWLEDGMENTS

To professors Frank B. Cross, Henry S. Fitch, and Richard F. Johnston
of the Department of Zoology of the University of Kansas I am grateful
for comments and suggestions in various phases of the study and the
preparation of the manuscript. Professor Johnston also made available
data on the breeding of the Bell Vireo from the files of the Kansas
Ornithological Society. I am indebted to my wife, Judith Barlow, for
many hours of typing and copy reading. Mrs. Lorna Cordonnier prepared
the map, Thomas H. Swearingen drew the histograms, and Professor A. B.
Leonard photographed and developed the histograms. Dr. Robert M.
Mengel contributed the sketch of the Bell Vireo and George P. Young
prepared the dummy Bell Vireo used in the field work. Thomas R.
Barlow, Donald A. Distler, Abbot S. Gaunt, John L. Lenz, Gary L.
Packard, A. Wayne Wiens, and John Wellman assisted in various phases
of the field work.

METHODS OF STUDY

Daily observations were made from May 11 to June 26 in 1959 and from
April 15 through July 15 in 1960. Six additional visits were made to
the study area in September of 1959, and ten others in July and
August, 1960. Periods of from one hour to eleven hours were spent in
the field each day, and a total of about five hundred hours were
logged in the field.

Each territory was visited for at least five minutes each day but more
often for twenty minutes. The breeding activities of the pairs were
rarely synchronous. Consequently several stages in the cycle of
building were simultaneously available for study.

Nine young and one adult were banded in 1959. No Bell Vireos were
banded in 1960. Individual pairs could be recognized because of their
exclusive use of