Early in the investigation it became apparent that there were differences between the species' feeding habits other than those of feeding zones.
Subjectively, the black-throated green appeared "nervous," the bay-breasted slow and "deliberate." In an attempt to make these observations objective,
the following measurements were taken on feeding birds. When a bird landed after a flight, a count of seconds was begun and continued until the bird
was lost from sight. The total number of flights
(visible uses of the wing) during this period was
recorded so that the mean interval between uses
of the wing could be computed.