1907
April 29
  Forenoon cloudy and showery. Afternoon clear
and warm with light S. wind.
  When I reached Ball Hill at 9.45 this morning
(from Cambridge) the oak woods on its southern slope
were alive with Yellow-rump and Yellow Palm Warblers.
I found many others later in the day in Pine Park
and on Pine Ridge, seeing in all at least fifty birds
of each species. Whenever I met with them they were
mingled together in about equal numbers keeping, as a
such, to the trees in rather dense growth and often
among pines although I noted a few of the Yellow
Palm Warblers on or near the ground in open places.
Both species sang freely through the forenoon. They
fed chiefly by flying out or upward from the
branches and capturing their insect prey in mid
air. It was easy to distinguish the Yellow Palm
Warblers, even at a distance by the ceaseless wagging
of their tails. Their songs varied greatly with different
individuals but all the forms I heard were dry
and unmusical. Some of them reminded me of
the song of Wilson's Black-cap. I should characterize
the usual form of song as a listless chatter. Sometimes
it was abrupt and explosive in character; sometimes
leisurely and halting or stuttering. The birds sang
in the intervals between their flittings from branch
to branch making no fuss about it although their
throats & tails pulsated & quivered as they gave utterance
to their feeble notes.