Concord, Mass.
1902.
April 10
(No 2)
  My walk back to the cabin this evening proved 
exceptionally interesting. It was nearly six o'clock
when I started. The mist-laden air seemed
comparatively warm but this was perhaps due chiefly
to the fact that the wind had lulled to a mere 
breath. Robins were singing in every direction, far
and near. There seemed to be a dozen or more
of them calling and a few singing, among the dense
pines behind Ball's Hill.
  As I was passing through Birch Field two
Great Horned Owls began hooting. They kept it
up for about ten minutes during which I remained
in one spot listening to them. One which was
evidently in Lawrence's pine woods beyond the Green
Field regularly uttered five notes ( hoo, hoo-hoo, hoo, hoo )
in slow, measured, impressive tones. The voice of the
other bird was pitched much higher and the eight
notes which he invariably uttered (hoo,hoo-hoo-hoo,
hoo-hoo-hoo,hoo) were given more rapidly. I have
repeatedly noticed a similar difference in the number
and arrangement of notes when two of these owls
are answering one another and I believe that one
form is characteristic of one sex and the other
of the opposite sex although I have no impression
as to which is peculiar to the male and which to 
the female. On this occasion the deep-voiced bird
with but five notes invariably hooted first. The
other always began hooting immediately after the 
first had ceased and several times it cut in on
the latter before it had finished its hoot.
Hooting of Great Horned Owls
49