Concord, Mass.
1908
April 1
(No 2)
  Yesterday forenoon I saw my first Cooper's Hawk,
a small male flying rather high over the run at the Farm.
To-day, about the same hour, what was no doubt the
same bird appeared over the run flying low and in a 
peculiar manner, flapping his wings slowly and with
long, deep sweeps each one of which seemed to lift
his body slightly. Thus his course was slightly
undulating with every now and then a longer and
deeper downward dip that carried him down almost
to the top of the trees. There was something about
this flight which reminded me of that of a butterfly.
It was not perfectly straight but curving slightly
towards the left. Whenever the bird swept directly
downward he uttered five or six shrill but rather
feeble screams which I should render kee, kee, kee,
kee, kee. I have seen this flight and heard these
notes only two or three times before. The calls are
very like those which the male Marsh Hawk makes
when "plunging" in early spring. I have little doubt
that they represent the love notes of the male Cooper's
Hawk. I saw no other bird to-day but the
female may have been hidden somewhere among
the trees.
Love notes & love flights of male Cooper Hawk
  Just before sunset the Bluebirds were singing
divinely in several directions. I saw a pair of them
eating barberries a little later. I cannot recall ever
seeing them thus engaged when the weather was fine
and the fields free from snow or frost.
Bluebirds eating barberries